1.Enostosis:

**Figure 4.**

**Figure 5.**

*cyst.*

**28**

*Aneurysmal Bone Cyst: Lateral radiograph of the left tibia (A) shows a well-circumscribed, expansile, lytic lesion (white arrow) involving the proximal tibial metadiaphysis. It demonstrates internal heterogeneity and has a narrow zone of transition. Coronal T1-weighted image (B) reveals the multiloculated appearance of the lesion (white arrow) and a predominantly intermediate T1 signal. No associated soft tissue swelling is noted. Sagittal fat-saturated T2-weighted image (C) shows multiple fluid-fluid levels within the lesion (yellow*

*Aneurysmal Bone Cyst: Lateral radiograph of the pelvis (A) shows an expansile, circumscribed, lytic, proximal femoral metaphyseal lesion (white arrow) with scalloped margins. On axial fat-saturated T2-weighted imaging (B), the lesion shows multiple fluid-fluid levels within (yellow arrow), suggesting an aneurysmal bone cyst. C and D are images of an aneurysmal bone cyst in the left pubic bone in a different patient. The aneurysmal bone cyst appears as a well-circumscribed lytic lesion on CT (C). Coronal T1-weighted fatsaturated post-contrast image (D) depicts heterogeneous and peripheral enhancement of the aneurysmal bone*

*arrows), a characteristic imaging feature of an aneurysmal bone cyst.*

*Recent Advances in Bone Tumours and Osteoarthritis*

Enostosis, also known as the bone island, is a benign focus of compact (cortical) bone located within the cancellous bone (medullary cavity). The bone island is most commonly found incidentally. Pathologically, a bone island is a normal cortical bone containing Haversian canals. There are radiations of cortical bone blending into the normal cancellous bone at the periphery of the lesion. The bone island is likely developmental, a normal cortical bone that fails to resolve during the growth process of endochondral ossification. The bone island is seen in adults far more frequently than children. There is no gender predilection. The bone island is generally a radiographic diagnosis. The bone island is a homogeneously dense lesion on radiography, fading at the periphery and merging into normal marrow. The periphery of the bone island is described as brush-like; may appear somewhat stellate [16] (**Figure 6A**). There is no associated cortical destruction. Polyostotic bone islands concentrated in the metaphyseal region are termed

#### **Figure 6.**

*Enostosis: Frontal radiograph of left humerus (A) shows a circumscribed focal sclerosis (white arrow) in the proximal epiphysis with peripheral brush border extensions into the normal adjacent bone. Axial T1-weighted (B) and T2-weighted fat-saturated (C) images reveal marked hypointense signal of the bone island.*

osteopoikilosis. Multiple sclerotic bone lesions can also be seen in patients with tuberous sclerosis complex [17].

On CT scan, enostosis is a sclerotic lesion with peripheral brush border extensions into the normal adjacent bone. Enostosis generally has a mean CT attenuation above 885 Hounsfield units (HU), whereas untreated osteoblastic metastases have mean CT attenuation below 885 HU, according to one study [18]. On MRI, the enostosis demonstrates low signal on all sequences with characteristic peripheral brush border extension into the normal bone (**Figure 6B** and **C**). There is no postcontrast enhancement. On nuclear medicine scintigraphy, if the lesion size is more than 1 cm, increased radiotracer uptake is related to the osteoblastic activity. SPECT CT has a sensitivity of up to 90% in detecting sclerotic bone metastases [19]. No treatment is required for enostosis.

### 2.Osteoma:

Osteoma is a benign tumor that demonstrates well-differentiated bone formation without aggressive features. Synonyms of osteoma include surface osteoma, parosteal osteoma, ivory osteoma, Ivory exostosis, and hamartoma of bone. Pathologically, osteoma is a hard white dense cortical bone. Many osteomas demonstrate a mixture of bone types. Osteomas may contain cancellous (trabecular, spongy) regions with a thin trabecular architecture with fatty marrow; woven bone with a fairly mature matrix with prominent collagen fibers; and lamellar (compact regions), which have narrow parallel layers of mature bone matrix. Most commonly, osteomas are found incidentally, with less than 5% of osteomas are symptomatic. The symptoms may be related to the mass effect upon the adjacent soft tissue structures, including proptosis, diplopia, sinusitis, mucocele, abscess as a complication of sinus blockage. Osteoma affects all age groups, including children, although most commonly diagnosed in the fourth and fifth decades of life [20]. The male to female ratio is 2:1. More than 75% of osteomas are seen in paranasal sinuses. The most common paranasal sinus affected is the frontal sinus (80% cases) [21]. Gardner syndrome has a known association with osteoma. Gardner syndrome is an autosomal dominant condition in which the patient may also have multiple cutaneous and subcutaneous lesions (cyst, fibromas), desmoid tumors, and multiple colonic polyps (colonic polyps in Gardner's syndrome have a marked propensity to develop adenocarcinoma).

in the patients with osteoid osteoma [24]. The osteoid osteoma contains a central region of vascularized connective tissue that contains osteoblasts and microtrabecular arrays lined by plump appositional osteoblasts. Around the central region, there is a hypervascular sclerotic bone and an abrupt interface between the central lesion and surrounding sclerosis. Osteoid osteoma is relatively common, comprising 5% of all bone tumors and 11% of all benign bone tumors [25]. The most common age range is 10–25 years with a male predilection (Male: female is 3:1) [26]. The classic clinical presentation includes pain, which worsens at night and is relieved by nonsteroidal antiinflammatory drugs. There is a gradual worsening of the pain over time. Intracapsular lesions may present with signs of synovitis, joint pain, and decreased range of motion. The spinal osteoid osteoma may present with painful nonrotatory scoliosis and concave to the lesion's side [27]. The most common location is cortical diaphyseal, in 65–70% of cases. The most common site involved is femur and tibia, which collectively account for 60% of osteoid

*Osteoma: Sagittal image (bone algorithm, A) and coronal image (bone window, B) of the paranasal sinuses reveal a compact and trabecular sclerotic polypoidal osteoma (black arrows) in the left ethmoid and sphenoid sinuses, extending into the left maxillary sinus with associated occlusion of left osteomeatal unit and left maxillary sinusitis (asterisk). Osteoma can also present as a less dense mass, as depicted by the rounded heterogeneous dense mass in the left posterior ethmoid sinus on the axial CT image (C). Note the high Hounsfield*

**Figure 7.**

**31**

*unit of the osteoma (D).*

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

osteomas [28]. The nidus is generally less than 2 cm in size.

On radiography, osteoid osteoma appears as an oval lytic lesion located within

the dense cortical bone surrounding thickened sclerotic cortical bone (**Figure 8A** and **B**). CT scan helps diagnose and specify the lesion's location (whether cortical versus subperiosteal or medullary) (**Figure 8C** and **D**). CT

scan is also helpful to guide percutaneous radiofrequency ablation or cryoablation. The nidus is a round lesion on MRI, slightly hyperintense to muscle on T1-weighted images and hyperintense on T2-weighted images. There is avid arterial phase enhancement of the nidus following contrast administration (**Figure 8E**). The surrounding cortical thickening and reaction is low signal intensity on all sequences. In nuclear medicine scintigraphy, the

In radiography and CT scan, the osteoma is seen as a homogeneous bone density lesion due to well-differentiated lamellar bone formation. The borders of osteomas are sharply demarcated (**Figure 7A**–**D**). There is no periosteal reaction. On MRI, osteomas are seen as low signal intensity on all sequences, without enhancement. Enhanced MRI or CT scan is best to evaluate complications such as mucocele, pneumatocele, or abscess. Treatment is required if intracranial or intraorbital extension, location near frontal sinus ostium, more than 50% of the frontal sinus filled by osteoma or unrelenting symptoms [22]. The endoscopic approach for resection is effective in lowgrade osteomas. In particular, the open approach, the osteoplastic flap approach, is well tolerated for resection of higher grade osteomas [23].

#### 3.Osteoid Osteoma:

Osteoid osteoma is a benign tumor of osteoblastic origin. The osteoid osteoma is often called "nidus" to distinguish it from surrounding reactive sclerosis from host response. There may be a genetic basis in chromosome band 22q13

#### **Figure 7.**

osteopoikilosis. Multiple sclerotic bone lesions can also be seen in patients

(**Figure 6B** and **C**). There is no postcontrast enhancement. On nuclear medicine scintigraphy, if the lesion size is more than 1 cm, increased radiotracer uptake is related to the osteoblastic activity. SPECT CT has a sensitivity of up to 90% in detecting sclerotic bone metastases [19]. No treatment is required for enostosis.

Osteoma is a benign tumor that demonstrates well-differentiated bone formation without aggressive features. Synonyms of osteoma include surface osteoma, parosteal osteoma, ivory osteoma, Ivory exostosis, and hamartoma of bone. Pathologically, osteoma is a hard white dense cortical bone. Many osteomas demonstrate a mixture of bone types. Osteomas may contain cancellous (trabecular, spongy) regions with a thin trabecular architecture with fatty marrow; woven bone with a fairly mature matrix with prominent collagen fibers; and lamellar (compact regions), which have narrow parallel

layers of mature bone matrix. Most commonly, osteomas are found

syndrome have a marked propensity to develop adenocarcinoma).

without enhancement. Enhanced MRI or CT scan is best to evaluate complications such as mucocele, pneumatocele, or abscess. Treatment is required if intracranial or intraorbital extension, location near frontal sinus ostium, more than 50% of the frontal sinus filled by osteoma or unrelenting symptoms [22]. The endoscopic approach for resection is effective in lowgrade osteomas. In particular, the open approach, the osteoplastic flap approach, is well tolerated for resection of higher grade osteomas [23].

In radiography and CT scan, the osteoma is seen as a homogeneous bone density lesion due to well-differentiated lamellar bone formation. The borders of osteomas are sharply demarcated (**Figure 7A**–**D**). There is no periosteal reaction. On MRI, osteomas are seen as low signal intensity on all sequences,

Osteoid osteoma is a benign tumor of osteoblastic origin. The osteoid osteoma is often called "nidus" to distinguish it from surrounding reactive sclerosis from host response. There may be a genetic basis in chromosome band 22q13

incidentally, with less than 5% of osteomas are symptomatic. The symptoms may be related to the mass effect upon the adjacent soft tissue structures, including proptosis, diplopia, sinusitis, mucocele, abscess as a complication of sinus blockage. Osteoma affects all age groups, including children, although most commonly diagnosed in the fourth and fifth decades of life [20]. The male to female ratio is 2:1. More than 75% of osteomas are seen in paranasal sinuses. The most common paranasal sinus affected is the frontal sinus (80% cases) [21]. Gardner syndrome has a known association with osteoma. Gardner syndrome is an autosomal dominant condition in which the patient may also have multiple cutaneous and subcutaneous lesions (cyst, fibromas), desmoid tumors, and multiple colonic polyps (colonic polyps in Gardner's

On CT scan, enostosis is a sclerotic lesion with peripheral brush border extensions into the normal adjacent bone. Enostosis generally has a mean CT attenuation above 885 Hounsfield units (HU), whereas untreated osteoblastic metastases have mean CT attenuation below 885 HU, according to one study [18]. On MRI, the enostosis demonstrates low signal on all sequences with characteristic peripheral brush border extension into the normal bone

with tuberous sclerosis complex [17].

*Recent Advances in Bone Tumours and Osteoarthritis*

2.Osteoma:

3.Osteoid Osteoma:

**30**

*Osteoma: Sagittal image (bone algorithm, A) and coronal image (bone window, B) of the paranasal sinuses reveal a compact and trabecular sclerotic polypoidal osteoma (black arrows) in the left ethmoid and sphenoid sinuses, extending into the left maxillary sinus with associated occlusion of left osteomeatal unit and left maxillary sinusitis (asterisk). Osteoma can also present as a less dense mass, as depicted by the rounded heterogeneous dense mass in the left posterior ethmoid sinus on the axial CT image (C). Note the high Hounsfield unit of the osteoma (D).*

in the patients with osteoid osteoma [24]. The osteoid osteoma contains a central region of vascularized connective tissue that contains osteoblasts and microtrabecular arrays lined by plump appositional osteoblasts. Around the central region, there is a hypervascular sclerotic bone and an abrupt interface between the central lesion and surrounding sclerosis. Osteoid osteoma is relatively common, comprising 5% of all bone tumors and 11% of all benign bone tumors [25]. The most common age range is 10–25 years with a male predilection (Male: female is 3:1) [26]. The classic clinical presentation includes pain, which worsens at night and is relieved by nonsteroidal antiinflammatory drugs. There is a gradual worsening of the pain over time. Intracapsular lesions may present with signs of synovitis, joint pain, and decreased range of motion. The spinal osteoid osteoma may present with painful nonrotatory scoliosis and concave to the lesion's side [27]. The most common location is cortical diaphyseal, in 65–70% of cases. The most common site involved is femur and tibia, which collectively account for 60% of osteoid osteomas [28]. The nidus is generally less than 2 cm in size.

On radiography, osteoid osteoma appears as an oval lytic lesion located within the dense cortical bone surrounding thickened sclerotic cortical bone (**Figure 8A** and **B**). CT scan helps diagnose and specify the lesion's location (whether cortical versus subperiosteal or medullary) (**Figure 8C** and **D**). CT scan is also helpful to guide percutaneous radiofrequency ablation or cryoablation. The nidus is a round lesion on MRI, slightly hyperintense to muscle on T1-weighted images and hyperintense on T2-weighted images. There is avid arterial phase enhancement of the nidus following contrast administration (**Figure 8E**). The surrounding cortical thickening and reaction is low signal intensity on all sequences. In nuclear medicine scintigraphy, the

osteoblasts, which are significantly larger than normal osteoblasts. Histologic differentiation between osteoblastoma and osteoid osteoma may be difficult. The most commonly affected age group is 1st through third decades, with the second decade being the most common [31]. Male:Female ratio is 2.5:1 [32]. The most common presenting symptom is dull, localized, gradually increasing pain. The patient may present with neurologic symptoms if cord or nerve root

compression is reported in approximately 50% of spinal lesions [33]. Approximately 30–40% of osteoblastoma occurs in the spine or flat bones [34]. In the spine, posterior elements are most frequently affected (in 94% of cases). The osteoblastoma is usually expanded on imaging, maybe bubbly with a thin cortex and variable degrees of mineralized matrix. There may be a sclerotic margin in the majority of the cases. Matrix ossification and thin cortical rim are more apparent on CT scan than x-ray (**Figure 9A**–**C**).

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

> On MRI, osteoblastoma is homogeneous low to intermediate signal on T1 weighted images and heterogeneous on fluid sensitive sequences depending on the degree of matrix ossification (**Figure 9D** and **E**). The enhancement ranges from mild to intense depending on the amount of matrix ossification. There may be associated extensive peripheral marrow edema and associated soft tissue edema due to the flare phenomenon [35] (**Figure 10A**–**C**). On nuclear medicine scintigraphy, osteoblastoma demonstrates intense focal

*Osteoblastoma: CT Head axial (A, B) and coronal (C) images in the bone window reveal a circumscribed, expansile, heterogeneous mixed lytic and sclerotic lesion (white arrows) involving the mastoid part of the left temporal bone and has an extradural intracranial component superiorly. Coronal T2-weighted image (D) of the brain at the level of mass (white arrows) reveals heterogenous increased T2 signal of the well-circumscribed*

*Osteoblastoma: Axial MR images of the lumbar spine shows an expansile mass lesion involving the left lamina and pedicle, encroaching in the spinal canal. It demonstrates heterogeneous hyperintense T2 signal (white arrow) with subtle fluid-fluid levels (A). The lesion shows an intermediate T1 signal (B) and shows heterogeneous enhancement as depicted in the T1-weighted post-contrast (C). The left posterior paraspinal*

*muscles demonstrate hyperintense T2 signal and post-contrast enhancement (black asterisks).*

*mass. Osteoblastoma (white arrow) shows an iso-to-hypointense T1 signal (E).*

**Figure 9.**

**Figure 10.**

**33**

#### **Figure 8.**

*Osteoid Osteoma: Frontal radiograph of the right femur (A) demonstrates an eccentric lucent area along the medial femoral neck cortex (black arrow) with marginal sclerosis (white arrow). Lateral radiographic view of the calcaneus (B) showing similar lesion with a central lucency surrounded by extensive sclerosis. Axial CT image on the same patient confirms the eccentric location of the lucency that shows an eccentric hyperdense focal speck within, suggesting nidus (C). Osteoid osteoma of the fibula in a different patient appears as a corticalbased lucency with nidus within (black arrow) on axial CT image (D). Axial post-contrast T1-weighted fatsaturated image (E) of the leg at the same level demonstrates enhancement of nidus (black arrow) and adjacent soft tissue.*

osteoid osteoma demonstrates intense round activity at the nidus, surrounded by less intensity of reactive bone, often termed as double density sign [29]. The round focus can help distinguish from a stress reaction, which has more linear activity. CT-guided radiofrequency ablation is most likely used to treat osteoid osteomas with an 85–90% initial success rate [30]. Larger or nonspherical lesions may require a second ablative procedure. The CT-guided ablation requires careful planning of an approach to avoid complications. Other alternatives include MR-guided laser ablation or ultrasound ablation.

4.Osteoblastoma:

Osteoblastoma is a rare benign bone-forming tumor, also known as giant osteoid osteoma. Pathologically, osteoblastoma contains elements of osteoid production in the form of active formation of osteoid and immature bone trabeculae. Aggressive osteoblastoma is characterized by epithelioid

## *Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

osteoblasts, which are significantly larger than normal osteoblasts. Histologic differentiation between osteoblastoma and osteoid osteoma may be difficult. The most commonly affected age group is 1st through third decades, with the second decade being the most common [31]. Male:Female ratio is 2.5:1 [32]. The most common presenting symptom is dull, localized, gradually increasing pain. The patient may present with neurologic symptoms if cord or nerve root compression is reported in approximately 50% of spinal lesions [33]. Approximately 30–40% of osteoblastoma occurs in the spine or flat bones [34]. In the spine, posterior elements are most frequently affected (in 94% of cases). The osteoblastoma is usually expanded on imaging, maybe bubbly with a thin cortex and variable degrees of mineralized matrix. There may be a sclerotic margin in the majority of the cases. Matrix ossification and thin cortical rim are more apparent on CT scan than x-ray (**Figure 9A**–**C**).

On MRI, osteoblastoma is homogeneous low to intermediate signal on T1 weighted images and heterogeneous on fluid sensitive sequences depending on the degree of matrix ossification (**Figure 9D** and **E**). The enhancement ranges from mild to intense depending on the amount of matrix ossification. There may be associated extensive peripheral marrow edema and associated soft tissue edema due to the flare phenomenon [35] (**Figure 10A**–**C**). On nuclear medicine scintigraphy, osteoblastoma demonstrates intense focal

#### **Figure 9.**

osteoid osteoma demonstrates intense round activity at the nidus, surrounded by less intensity of reactive bone, often termed as double density sign [29]. The round focus can help distinguish from a stress reaction, which has more linear activity. CT-guided radiofrequency ablation is most likely used to treat

nonspherical lesions may require a second ablative procedure. The CT-guided ablation requires careful planning of an approach to avoid complications. Other alternatives include MR-guided laser ablation or ultrasound ablation.

Osteoblastoma is a rare benign bone-forming tumor, also known as giant osteoid osteoma. Pathologically, osteoblastoma contains elements of osteoid production in the form of active formation of osteoid and immature bone trabeculae. Aggressive osteoblastoma is characterized by epithelioid

osteoid osteomas with an 85–90% initial success rate [30]. Larger or

*Osteoid Osteoma: Frontal radiograph of the right femur (A) demonstrates an eccentric lucent area along the medial femoral neck cortex (black arrow) with marginal sclerosis (white arrow). Lateral radiographic view of the calcaneus (B) showing similar lesion with a central lucency surrounded by extensive sclerosis. Axial CT image on the same patient confirms the eccentric location of the lucency that shows an eccentric hyperdense focal speck within, suggesting nidus (C). Osteoid osteoma of the fibula in a different patient appears as a corticalbased lucency with nidus within (black arrow) on axial CT image (D). Axial post-contrast T1-weighted fatsaturated image (E) of the leg at the same level demonstrates enhancement of nidus (black arrow) and adjacent*

*Recent Advances in Bone Tumours and Osteoarthritis*

4.Osteoblastoma:

**Figure 8.**

*soft tissue.*

**32**

*Osteoblastoma: CT Head axial (A, B) and coronal (C) images in the bone window reveal a circumscribed, expansile, heterogeneous mixed lytic and sclerotic lesion (white arrows) involving the mastoid part of the left temporal bone and has an extradural intracranial component superiorly. Coronal T2-weighted image (D) of the brain at the level of mass (white arrows) reveals heterogenous increased T2 signal of the well-circumscribed mass. Osteoblastoma (white arrow) shows an iso-to-hypointense T1 signal (E).*

#### **Figure 10.**

*Osteoblastoma: Axial MR images of the lumbar spine shows an expansile mass lesion involving the left lamina and pedicle, encroaching in the spinal canal. It demonstrates heterogeneous hyperintense T2 signal (white arrow) with subtle fluid-fluid levels (A). The lesion shows an intermediate T1 signal (B) and shows heterogeneous enhancement as depicted in the T1-weighted post-contrast (C). The left posterior paraspinal muscles demonstrate hyperintense T2 signal and post-contrast enhancement (black asterisks).*

uptake. Surgical excision, in particular, marginal excision (curettage), is most recommended if wide resection would results in functional impairment. Incomplete excision may result in recurrence (14–24% reported in different series) [36, 37]. Other treatment options include percutaneous thermal ablation. Sporadic cases of osteoblastoma degenerating to osteosarcoma have been reported [38].

Cartilage forming tumors:

1.**Enchondroma:** Enchondroma is a benign tumor of hyaline cartilage originating in the medullary bone. Enchondromas arise from growth plate cartilage rests and/or chondrocytes that subsequently proliferate and slowly enlarge and are composed of mature hyaline cartilage. The most common location of enchondroma is the medullary cavity of tubular bones. Enchondroma accounts for 12–24% of all benign bone tumors and 3–10% of all bone tumors [39, 40]. Approximately 35% of enchondromas occur in hands [40]. In long bones, the proximal humerus is the most common location. Enchondromas are usually detected incidentally on x-ray or MRI. The majority of enchondromas are detected in the third through fifth decades of life [41]. There is no gender predilection. Enchondroma is the most common tumor of the phalanges of the hand. The classic radiographic appearance of enchondroma in the long bones is a metaphyseal lesion with ring and arc type of chondroid mineralization without endosteal scalloping, cortical destruction, or soft tissue mass (**Figure 11A** and **B**). In phalanges, the enchondroma demonstrates an expansile lucent lesion with cortical thinning (**Figure 11D** and **E**). The phalangeal enchondroma may present with pathologic fracture. On MRI, the enchondroma demonstrates low to intermediate signal intensity on T1 weighted images and lobulated high signal on fluid sensitive sequences. Dynamic contrast-enhanced MRI may improve chances of differentiating enchondroma from low-grade chondrosarcoma [42]. Treatment is usually not required for small incidental lesions. For large symptomatic lesions, marginal and/or wide resection should be considered. Sarcoma follow-up surveillance is required if histologic findings showed low-grade chondrosarcoma.

Ollier disease is a nonhereditary, sporadic skeletal disorder characterized by multiple enchondromas principally located in the metaphyseal regions. If there are associated soft tissue hemangiomas, the syndrome is termed Maffucci syndrome [43]. In Ollier disease, the enchondromas demonstrate vertical streaks of lucencies in the columnar configuration, in metaphases of long bones, extending to the epiphysis [43] (**Figure 12B** and **C**). The phalangeal lesions are typically expansile with sharply defined scalloped margins (**Figure 12A**). There is an approximately 25–30% risk of chondrosarcoma in the setting of Ollier disease [44]. Corrective surgery is required if there are complications such as growth impairment, deformity such as leg length discrepancy.

common presenting symptom is mild localized pain, which refers to joint. The most common age range affected is 10–25 years old. Males are more frequently affected than females (nearly 2:1). Chondroblastoma comprises less than 1% of all

*Enchondroma: Frontal radiograph of the distal femur (A) and proximal femur (B) in two different patients reveal the characteristic rings and arcs pattern of chondroid mineralization (yellow arrows). The lateral radiograph of the forearm (C) shows an expansile lytic lesion (white arrow) in the mid-diaphysis of radius. It demonstrates a narrow zone of transition without any periosteal reaction or associated soft tissue swelling. A frontal radiographic view of the proximal phalanx of the little finger (D) shows a well-defined eccentric osteolytic lesion (white arrow). The frontal radiograph of the index finger (E) shows an expansile wellcircumscribed osteolytic lesion (white arrow) with a chondroid matrix. The black arrow points to a cortical*

bone tumors and approximately 9% of benign bone tumors [47]. The chondroblastoma is a geographic lytic lesion with sclerotic margins in most lesions on radiography and CT scan. The lesion may contain chondroid matrix calcifications. The lesions are eccentrically located within the epiphysis with extension into metadiaphysis as they enlarge. There may be an associated cortical expansion or thinning (**Figure 13A**–**C**). On MRI, the lesions are typically low signal on T1 and inhomogeneously high signal on fluid sensitive sequences. The inhomogeneity is related to the chondroid matrix, calcification, and fluid within the lesion [48] (**Figure 13D**–**F**). Curettage and bone grafting is the surgical treatment of choice. Radiofrequency ablation may be considered in small lesions.

**Figure 11.**

**35**

*breach concerning a pathological fracture.*

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

3.**Chondromyxoid fibroma:** Chondromyxoid fibroma is a benign lobulated cartilaginous tumor. Approximately 60% of chondromyxoid fibromas occur in long bones, with the proximal tibia being the single most frequent site. Genetic basis has been described in the literature in the form of clonal abnormalities of

2.**Chondroblastoma:** Chondroblastoma is a benign cartilage tumor arising in the epiphysis of skeletally immature individuals. More than 75% of chondroblastomas occur in long bones [45]. The most common location is epiphysis, with possible extension to metaphasis. Chondroblastoma may have a genetic basis in structural anomalies involving chromosomes 5 and 8 [46]. Macroscopically, there are nodules of relatively mature cartilage surrounded by highly cellular tissue. Giant cells are usually present in the tumor. The most

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

#### **Figure 11.**

uptake. Surgical excision, in particular, marginal excision (curettage), is most recommended if wide resection would results in functional impairment. Incomplete excision may result in recurrence (14–24% reported in different series) [36, 37]. Other treatment options include percutaneous thermal ablation. Sporadic cases of osteoblastoma degenerating to osteosarcoma have

1.**Enchondroma:** Enchondroma is a benign tumor of hyaline cartilage

the phalanges of the hand. The classic radiographic appearance of

required if histologic findings showed low-grade chondrosarcoma.

Ollier disease is a nonhereditary, sporadic skeletal disorder characterized by multiple enchondromas principally located in the metaphyseal regions. If there are associated soft tissue hemangiomas, the syndrome is termed Maffucci syndrome [43]. In Ollier disease, the enchondromas demonstrate vertical streaks of lucencies in the columnar configuration, in metaphases of long bones, extending to the epiphysis [43] (**Figure 12B** and **C**). The phalangeal lesions are typically expansile with sharply defined scalloped margins (**Figure 12A**). There is an approximately 25–30% risk of

chondrosarcoma in the setting of Ollier disease [44]. Corrective surgery is required if there are complications such as growth impairment, deformity

2.**Chondroblastoma:** Chondroblastoma is a benign cartilage tumor arising in the

chondroblastomas occur in long bones [45]. The most common location is epiphysis, with possible extension to metaphasis. Chondroblastoma may have a genetic basis in structural anomalies involving chromosomes 5 and 8 [46]. Macroscopically, there are nodules of relatively mature cartilage surrounded by highly cellular tissue. Giant cells are usually present in the tumor. The most

epiphysis of skeletally immature individuals. More than 75% of

such as leg length discrepancy.

**34**

originating in the medullary bone. Enchondromas arise from growth plate cartilage rests and/or chondrocytes that subsequently proliferate and slowly enlarge and are composed of mature hyaline cartilage. The most common location of enchondroma is the medullary cavity of tubular bones.

Enchondroma accounts for 12–24% of all benign bone tumors and 3–10% of all bone tumors [39, 40]. Approximately 35% of enchondromas occur in hands [40]. In long bones, the proximal humerus is the most common location. Enchondromas are usually detected incidentally on x-ray or MRI. The majority of enchondromas are detected in the third through fifth decades of life [41]. There is no gender predilection. Enchondroma is the most common tumor of

enchondroma in the long bones is a metaphyseal lesion with ring and arc type of chondroid mineralization without endosteal scalloping, cortical destruction, or soft tissue mass (**Figure 11A** and **B**). In phalanges, the enchondroma demonstrates an expansile lucent lesion with cortical thinning (**Figure 11D** and **E**). The phalangeal enchondroma may present with pathologic fracture. On MRI, the enchondroma demonstrates low to intermediate signal intensity on T1 weighted images and lobulated high signal on fluid sensitive sequences. Dynamic contrast-enhanced MRI may improve chances of differentiating enchondroma from low-grade chondrosarcoma [42]. Treatment is usually not required for small incidental lesions. For large symptomatic lesions, marginal and/or wide resection should be considered. Sarcoma follow-up surveillance is

been reported [38].

*Recent Advances in Bone Tumours and Osteoarthritis*

Cartilage forming tumors:

*Enchondroma: Frontal radiograph of the distal femur (A) and proximal femur (B) in two different patients reveal the characteristic rings and arcs pattern of chondroid mineralization (yellow arrows). The lateral radiograph of the forearm (C) shows an expansile lytic lesion (white arrow) in the mid-diaphysis of radius. It demonstrates a narrow zone of transition without any periosteal reaction or associated soft tissue swelling. A frontal radiographic view of the proximal phalanx of the little finger (D) shows a well-defined eccentric osteolytic lesion (white arrow). The frontal radiograph of the index finger (E) shows an expansile wellcircumscribed osteolytic lesion (white arrow) with a chondroid matrix. The black arrow points to a cortical breach concerning a pathological fracture.*

common presenting symptom is mild localized pain, which refers to joint. The most common age range affected is 10–25 years old. Males are more frequently affected than females (nearly 2:1). Chondroblastoma comprises less than 1% of all bone tumors and approximately 9% of benign bone tumors [47]. The chondroblastoma is a geographic lytic lesion with sclerotic margins in most lesions on radiography and CT scan. The lesion may contain chondroid matrix calcifications. The lesions are eccentrically located within the epiphysis with extension into metadiaphysis as they enlarge. There may be an associated cortical expansion or thinning (**Figure 13A**–**C**). On MRI, the lesions are typically low signal on T1 and inhomogeneously high signal on fluid sensitive sequences. The inhomogeneity is related to the chondroid matrix, calcification, and fluid within the lesion [48] (**Figure 13D**–**F**). Curettage and bone grafting is the surgical treatment of choice. Radiofrequency ablation may be considered in small lesions.

3.**Chondromyxoid fibroma:** Chondromyxoid fibroma is a benign lobulated cartilaginous tumor. Approximately 60% of chondromyxoid fibromas occur in long bones, with the proximal tibia being the single most frequent site. Genetic basis has been described in the literature in the form of clonal abnormalities of

#### **Figure 12.**

*Ollier's disease: Frontal radiograph of the left hand (A) demonstrates multiple circumscribed lucent areas (white arrows) in hand with a sharp zone of transition. Frontal radiograph of the right femur (B) shows vertical streaks of lucencies (black arrows) extending from diaphysis towards epiphysis. Frontal radiograph of the right tibia and fibula (C) reveals an expansile enchondroma in the proximal fibular metaphysis (white arrows) and a not that much expansile enchondroma in the tibial metadiaphysis.*

geographic with sclerotic margins. The lesions typically occur in metaphysis or

Approximately 60% of lesions are eccentric, with evidence of lobulation and thinning of the cortex (**Figure 14A** and **B**). Pseudotrabeculations within the lesion give the appearance of septations [49]. There is an absence of periosteal reaction without pathologic fracture. On MRI, the lesion is typically isointense to skeletal muscle on T1-weighted images, and on fluid sensitive sequences, the lesion is centrally hyperintense with a peripheral band of intermediate signal. There is a peripheral nodular enhancement or diffuse postcontrast enhancement [50] (**Figure 14C**–**E**). The lesions are typically treated with marginal excision with curettage and bone grafting. The recurrence rate is

diaphysis, which are oriented along the longitudinal axis of the bone.

*features to support the diagnosis of the chondromyxoid fibroma (CMF).*

*Chondromyxoid fibroma: Bone window (A) and soft tissue window (B) axial CT head images show a welldefined lobulated lytic lesion (white arrows) involving the mastoid and petrous parts of the right temporal bone and clivus. A note is made of the low attenuation value of the CMF lesion and absent calcifications. On the T2 weighted image (C), the CMF lesion demonstrates a peripheral hypointense sclerotic rim with an intrinsic high signal (white arrow). It shows a hypointense T1 signal (D) and shows thick peripheral enhancement (E). MR*

4.**Osteochondroma:** Osteochondroma is cartilage capped exostosis with continuous cortex and marrow extending from the underlying bone. Osteochondroma most commonly arises from metaphysis or metaphyseal equivalents. Approximately 95% of them are located in extremities; the femur is most commonly affected [52]. Microscopically, the inner layer is composed of normal bone; the middle layer is composed of cartilage cap with superficial clusters of chondrocytes, and the outer layer is composed of perichondrium, which is continuous with the periosteum of the underlying bone. The most common presenting symptom is a chronically present hard swelling. It may present as mechanical pain from trauma or impingement. Vascular complications include pseudoaneurysm formation and arterial or venous stenosis/thrombosis. Increasing pain and/or mass enlargement following skeletal maturation suggest degeneration to chondrosarcoma [53]. Osteochondromas could be sessile or pedunculated. On radiography and CT scan, the pedunculated osteochondroma

approximately 3–22% [51].

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

**Figure 14.**

**37**

#### **Figure 13.**

*Chondroblastoma: Frontal radiographic view of the left pelvis (A) shows a calcified mass of the left ischium and pubic bones. Coronal bone window (B) and axial soft tissue window (C) images demonstrate an expansile osteolytic lesion (white arrows) with a well-defined lobulated margin and chondroid matrix (black arrow). Chondroblastoma demonstrates a hypointense T1 signal (white arrow; D) with a peripheral sclerotic rim. Coronal (E) and axial (F) T2-weighted fat-saturated images reveal heterogeneous hyperintense T2 signal of the mass (white arrows) with extensive peritumoral edema.*

chromosome 6 and pronounced expression of type II collagen, which is unique compared with other cartilaginous lesions. Microscopically, the lesion is lobular with stellate cells in the myxoid background. The most common presenting symptom is mild chronic pain. The mean age of presentation is 23 years, with 50 percent of patients are in the second decade at presentation. There is slight medial predominance. On radiography and CT, the lesions are

#### **Figure 14.**

*Chondromyxoid fibroma: Bone window (A) and soft tissue window (B) axial CT head images show a welldefined lobulated lytic lesion (white arrows) involving the mastoid and petrous parts of the right temporal bone and clivus. A note is made of the low attenuation value of the CMF lesion and absent calcifications. On the T2 weighted image (C), the CMF lesion demonstrates a peripheral hypointense sclerotic rim with an intrinsic high signal (white arrow). It shows a hypointense T1 signal (D) and shows thick peripheral enhancement (E). MR features to support the diagnosis of the chondromyxoid fibroma (CMF).*

geographic with sclerotic margins. The lesions typically occur in metaphysis or diaphysis, which are oriented along the longitudinal axis of the bone. Approximately 60% of lesions are eccentric, with evidence of lobulation and thinning of the cortex (**Figure 14A** and **B**). Pseudotrabeculations within the lesion give the appearance of septations [49]. There is an absence of periosteal reaction without pathologic fracture. On MRI, the lesion is typically isointense to skeletal muscle on T1-weighted images, and on fluid sensitive sequences, the lesion is centrally hyperintense with a peripheral band of intermediate signal. There is a peripheral nodular enhancement or diffuse postcontrast enhancement [50] (**Figure 14C**–**E**). The lesions are typically treated with marginal excision with curettage and bone grafting. The recurrence rate is approximately 3–22% [51].

4.**Osteochondroma:** Osteochondroma is cartilage capped exostosis with continuous cortex and marrow extending from the underlying bone. Osteochondroma most commonly arises from metaphysis or metaphyseal equivalents. Approximately 95% of them are located in extremities; the femur is most commonly affected [52]. Microscopically, the inner layer is composed of normal bone; the middle layer is composed of cartilage cap with superficial clusters of chondrocytes, and the outer layer is composed of perichondrium, which is continuous with the periosteum of the underlying bone. The most common presenting symptom is a chronically present hard swelling. It may present as mechanical pain from trauma or impingement. Vascular complications include pseudoaneurysm formation and arterial or venous stenosis/thrombosis. Increasing pain and/or mass enlargement following skeletal maturation suggest degeneration to chondrosarcoma [53]. Osteochondromas could be sessile or pedunculated. On radiography and CT scan, the pedunculated osteochondroma

chromosome 6 and pronounced expression of type II collagen, which is unique compared with other cartilaginous lesions. Microscopically, the lesion is lobular with stellate cells in the myxoid background. The most common presenting symptom is mild chronic pain. The mean age of presentation is 23 years, with 50 percent of patients are in the second decade at presentation. There is slight medial predominance. On radiography and CT, the lesions are

*Chondroblastoma: Frontal radiographic view of the left pelvis (A) shows a calcified mass of the left ischium and pubic bones. Coronal bone window (B) and axial soft tissue window (C) images demonstrate an expansile osteolytic lesion (white arrows) with a well-defined lobulated margin and chondroid matrix (black arrow). Chondroblastoma demonstrates a hypointense T1 signal (white arrow; D) with a peripheral sclerotic rim. Coronal (E) and axial (F) T2-weighted fat-saturated images reveal heterogeneous hyperintense T2 signal of the*

*Ollier's disease: Frontal radiograph of the left hand (A) demonstrates multiple circumscribed lucent areas (white arrows) in hand with a sharp zone of transition. Frontal radiograph of the right femur (B) shows vertical streaks of lucencies (black arrows) extending from diaphysis towards epiphysis. Frontal radiograph of the right tibia and fibula (C) reveals an expansile enchondroma in the proximal fibular metaphysis (white*

*arrows) and a not that much expansile enchondroma in the tibial metadiaphysis.*

*Recent Advances in Bone Tumours and Osteoarthritis*

**Figure 12.**

**Figure 13.**

**36**

*mass (white arrows) with extensive peritumoral edema.*

demonstrates a narrow stalk with cauliflower exostosis (**Figure 15D**), and the sessile osteochondroma is broad-based (**Figure 15A** and **C**). If near the joint, osteochondroma tends to project away from the joint line, growing along the forces generated by the location of the tendons and ligaments. The pelvic osteochondromas could become very large before discovery. Rib lesions may present with pneumothorax. Endochondral calcification may be seen within the cartilage cap and medullary bone as the rings and arcs, punctate or flocculant calcification. The overlying cartilage cap is generally thinned, not evaluated by radiograph. Degeneration of the lesion to chondrosarcoma is suggested by osseous destruction, change in calcifications, or enlargement of the cartilage cap as evidenced by distortion of the fat planes. On MRI, the cortex of the lesion is contiguous with the underlying bone. The overlying hyaline cartilage cap has a lobulated high signal on fluid-sensitive sequences covered by thin perichondrium and demonstrates a low signal on T1 and T2 sequences [54] (**Figure 15E** and **F**). Surgical resection of the osteochondroma is recommended when the cartilage cap thickness is greater than 1 cm. In one study, the use of 2 cm as a cutoff for distinguishing benign osteochondromas from secondary chondrosarcomas provided sensitivities, specificities, positive predictive values, and negative predictive values of 100%, 98%, 96%, and 100%, respectively, for MR imaging and 100%, 95%, 93%, and 100%, respectively, for CT [54]. Treatment is mostly watchful waiting. Resection of the osteochondroma is recommended when there are mechanical complications such as bursa formation, nerve irritation, or impingement. Resection of the entire perichondrium is required to avoid recurrence. Chondrosarcoma is typically treated by wide surgical resection.

are more common than pedunculated osteochondromas. There is an approximately 3–5% incidence of degeneration to chondrosarcoma [56]. Radiography is the 1st line modality to evaluate for this condition. MRI can be performed to evaluate the thickness of the cartilage cap and evaluate for complications from the mass effect. If the lesion is superficial, ultrasound can also be used to evaluate for thickness and irregularity of the cartilage cap. Surgical resection is performed if there are complications from mass effect or

*Trevor disease: Frontal radiograph of the right shoulder demonstrates an osteochondroma arising from right proximal humeral epiphysis, suggesting Trevor Disease (A). Sagittal bone window image of ankle demonstrates*

Trevor disease, also known as dysplasia epiphysealis hemimelica, is an extremely rare, nonhereditary disease in which the osteochondromas arise from the epiphysis. It affects approximately one in 1 million population [57]. Only one epiphysis is involved in the localized type, although multiple epiphyses are affected involving the entire extremity in generalized type. There is the presence of an exostosis arising from the epiphysis on

radiography and CT scan (**Figure 16A** and **B**). Surgical excision of mass is

5.**Juxtacortical chondroma:** Juxtacortical chondroma is a chondroid tumor arising in the periosteal layer of tubular bones. It is a rare benign tumor comprising less than 2% of chondromas [58]. The most common age range affected is second through fourth decades. Although, it may occur in children. Juxtacortical chondroma is a surface lesion arising from the metaphysis of the tubular bone-producing chondroid matrix. The lesion is located in the proximal humerus and femur in 70% of cases. On radiography, there is saucerization of the cortex with sclerotic margins and matrix calcification (in 75% of cases) (**Figure 17A**). There may be associated soft tissue mass. On MRI, the lesion is lobulated with iso to hypointense T1 signal and hyperintense T2 signal with heterogeneous predominantly peripheral enhancement (**Figure 17B**–**E**). The tumor demonstrates slow local progression. Wide surgical excision is the most

appropriate treatment for lesions greater than 3 cm in size [59].

1.**Fibrous cortical defect:** Fibrous cortical defect is the most common benign bone lesion [60]. The most common location is usually metaphysis or

evidence of degeneration to chondrosarcoma.

usually performed to preserve the joint.

Fibro-osseous lesions:

**39**

**Figure 16.**

*an osteochondroma arising from Talus (B).*

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

Multiple hereditary exostoses, also known as diaphyseal aclasis, is an autosomal dominant condition in which there are multiple sessile and pedunculated osteochondromas. Approximately 90% of patients have a positive family history of this condition [55]. There is a symmetric widening of the metaphysis with the normal underlying bone. Sessile osteochondromas

#### **Figure 15.**

*Osteochondroma: Axial CT bone algorithm image (A) of the mid thorax shows a focal bulge in the anterior right rib (white arrow) with cortical continuity, a finding also appreciated on the longitudinal grayscale ultrasound image (B). It represents a sessile osteochondroma, another example of which is C (white arrow). Frontal radiograph of the left tibia (D) reveals a pedunculated osteochondroma (white arrow) noted in the metaphyseal region, with the cortex of the parent bone (tibia in this case) contiguous with that of the lesion, and the lesion is directed away from the joint. The T2-weighted fat-saturated coronal (E) and axial (F) images reveal the T2 hyperintense cartilage cap (yellow arrows) of that osteochondral lesion (white arrows).*

## **Figure 16.**

demonstrates a narrow stalk with cauliflower exostosis (**Figure 15D**), and the sessile osteochondroma is broad-based (**Figure 15A** and **C**). If near the joint, osteochondroma tends to project away from the joint line, growing along the forces generated by the location of the tendons and ligaments. The pelvic osteochondromas could become very large before discovery. Rib lesions may present with pneumothorax. Endochondral calcification may be seen within the cartilage cap and medullary bone as the rings and arcs, punctate or flocculant calcification. The overlying cartilage cap is generally thinned, not evaluated by radiograph. Degeneration of the lesion to chondrosarcoma is suggested by osseous destruction, change in calcifications, or enlargement of the cartilage cap as evidenced by distortion of the fat planes. On MRI, the cortex of the lesion is contiguous with the underlying bone. The overlying hyaline cartilage cap has a

lobulated high signal on fluid-sensitive sequences covered by thin

perichondrium and demonstrates a low signal on T1 and T2 sequences [54] (**Figure 15E** and **F**). Surgical resection of the osteochondroma is recommended when the cartilage cap thickness is greater than 1 cm. In one study, the use of 2 cm as a cutoff for distinguishing benign osteochondromas from secondary chondrosarcomas provided sensitivities, specificities, positive predictive values, and negative predictive values of 100%, 98%, 96%, and 100%, respectively, for MR imaging and 100%, 95%, 93%, and 100%, respectively, for CT [54]. Treatment is mostly watchful waiting. Resection of the osteochondroma is recommended when there are mechanical complications such as bursa formation, nerve irritation, or impingement. Resection of the entire

perichondrium is required to avoid recurrence. Chondrosarcoma is typically

Multiple hereditary exostoses, also known as diaphyseal aclasis, is an autosomal dominant condition in which there are multiple sessile and pedunculated osteochondromas. Approximately 90% of patients have a positive family history of this condition [55]. There is a symmetric widening of the metaphysis with the normal underlying bone. Sessile osteochondromas

*Osteochondroma: Axial CT bone algorithm image (A) of the mid thorax shows a focal bulge in the anterior right rib (white arrow) with cortical continuity, a finding also appreciated on the longitudinal grayscale ultrasound image (B). It represents a sessile osteochondroma, another example of which is C (white arrow). Frontal radiograph of the left tibia (D) reveals a pedunculated osteochondroma (white arrow) noted in the metaphyseal region, with the cortex of the parent bone (tibia in this case) contiguous with that of the lesion, and the lesion is directed away from the joint. The T2-weighted fat-saturated coronal (E) and axial (F) images reveal the T2 hyperintense cartilage cap (yellow arrows) of that osteochondral lesion (white arrows).*

treated by wide surgical resection.

*Recent Advances in Bone Tumours and Osteoarthritis*

**Figure 15.**

**38**

*Trevor disease: Frontal radiograph of the right shoulder demonstrates an osteochondroma arising from right proximal humeral epiphysis, suggesting Trevor Disease (A). Sagittal bone window image of ankle demonstrates an osteochondroma arising from Talus (B).*

are more common than pedunculated osteochondromas. There is an approximately 3–5% incidence of degeneration to chondrosarcoma [56]. Radiography is the 1st line modality to evaluate for this condition. MRI can be performed to evaluate the thickness of the cartilage cap and evaluate for complications from the mass effect. If the lesion is superficial, ultrasound can also be used to evaluate for thickness and irregularity of the cartilage cap. Surgical resection is performed if there are complications from mass effect or evidence of degeneration to chondrosarcoma.

Trevor disease, also known as dysplasia epiphysealis hemimelica, is an extremely rare, nonhereditary disease in which the osteochondromas arise from the epiphysis. It affects approximately one in 1 million population [57]. Only one epiphysis is involved in the localized type, although multiple epiphyses are affected involving the entire extremity in generalized type. There is the presence of an exostosis arising from the epiphysis on radiography and CT scan (**Figure 16A** and **B**). Surgical excision of mass is usually performed to preserve the joint.

5.**Juxtacortical chondroma:** Juxtacortical chondroma is a chondroid tumor arising in the periosteal layer of tubular bones. It is a rare benign tumor comprising less than 2% of chondromas [58]. The most common age range affected is second through fourth decades. Although, it may occur in children. Juxtacortical chondroma is a surface lesion arising from the metaphysis of the tubular bone-producing chondroid matrix. The lesion is located in the proximal humerus and femur in 70% of cases. On radiography, there is saucerization of the cortex with sclerotic margins and matrix calcification (in 75% of cases) (**Figure 17A**). There may be associated soft tissue mass. On MRI, the lesion is lobulated with iso to hypointense T1 signal and hyperintense T2 signal with heterogeneous predominantly peripheral enhancement (**Figure 17B**–**E**). The tumor demonstrates slow local progression. Wide surgical excision is the most appropriate treatment for lesions greater than 3 cm in size [59].

Fibro-osseous lesions:

1.**Fibrous cortical defect:** Fibrous cortical defect is the most common benign bone lesion [60]. The most common location is usually metaphysis or

metadiaphysis junction of the femur or tibia. On radiographs, the fibrous cortical defects are eccentric cortically based lucent lesions with mineralized rim (**Figure 18A** and **B**). There is no involvement of the underlying medullary cavity. There is no periosteal reaction. The fibrous cortical defects are typically hypointense on T1 weighted images and hyperintense on T2-weighted images (**Figure 18C** and **D**). The signal intensity depends on the stage of healing. Fibrous cortical defects are typically seen incidentally on radiographs. These are no-touch lesions (no treatment is required). Benign fibro-osseous lesions may be metabolically active on FDG PET CT exam and should not be confused with metastases [61].

2.**Nonossifying fibroma:** Nonossifying fibroma is a benign fibrous lesion composed of spindle cells in a collagenous matrix. Nonossifying fibroma is generally greater than 3 cm in greatest dimension (as opposed to a fibrous cortical defect less than 3 cm in diameter) [62]. Nonossifying fibroma typically originates in the metaphysis and is cortically based, most commonly found around the knee and distal tibia. It can be multifocal in 8% of cases. Multifocal nonossifying fibromas may be associated with neurofibromatosis (Jaffe-Campanacci syndrome). Nonossifying fibroma is usually asymptomatic; however, it could present with pathological fracture. It is typically seen in the

Radiographic and CT appearance depends on the morphologic age of the lesion. Initially, the lesion appears as a lytic, geographic area with a thin sclerotic margin (**Figure 19A** and **B**). During early filling phases, it has a thicker sclerotic margin forming peripheral bone. During late stages, the lesion may be entirely sclerotic with usual remodeling to normal bone type appearance. On MRI, the lesion is hypointense to skeletal muscle on T1 and heterogeneous on fluid sensitive sequences with low signal areas and hyperintense areas (**Figure 19C** and **D**). The regions of low signal areas are

fibrous elements and hemosiderin. There is peripheral and septal

3.**Fibrous Dysplasia**: Fibrous dysplasia (FD) is a developmental disorder characterized by the replacement of normal bone by immature bone and cartilaginous tissue. Most cases are sporadic and are related to a mutation in the GNAS1 gene. GNAS gene codes for the stimulatory alpha subunit of guanine nucleotide-binding protein, and its mutation result in persistent adenyl cyclase activation leading to osteoblastic proliferation. FD comprises

*Non-Ossifying Fibroma: Frontal and lateral radiographs of femur demonstrate an eccentric cortically based radiolucent lesion with sclerotic margin in distal meta-diaphysis (A, B). On MRI of the same patient, the lesion demonstrates predominantly hypointense signal on T1 and heterogenous signal on STIR due to fibrous elements*

enhancement following contrast administration. No cortical destruction or soft tissue mass lesion is demonstrated. No treatment is required in a vast majority of cases. If there is a risk for pathologic fracture due to the size of the lesion, curettage and bone grafting can be performed. Syndromic form of multiple nonossifying fibromas has a higher rate of recurrence after surgical

first and second decade of life.

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

removal [63].

**Figure 19.**

**41**

*and hemosiderin (C, D).*

#### **Figure 17.**

*Juxtacortical chondroma: Frontal radiograph of the left tibia and fibula (A) demonstrates a well-defined distal tibial metadiaphyseal lucent lesion (white arrow) with underlying cortical saucerization or scalloping(yellow arrows) and subjacent cortical sclerosis. It demonstrates a hypointense T1 signal (B) and an increased T2 signal (C). T1-weighted fat-saturated pre (D) and postcontrast (E) images demonstrate peripheral enhancement of the chondroma lesion (white arrow).*

#### **Figure 18.**

*Fibrous cortical defect: Frontal (A) and lateral (B) radiographs of distal femur demonstrate eccentric lucent intracortical defect (white arrows) outlined by a rim of sclerosis. Note that there is no involvement of the underlying medullary cavity, and there is no periosteal reaction. The lesion (white arrows) demonstrates a hypointense T1 signal (C) and increased T2 signal with a peripheral hypointense sclerotic rim (D).*

metadiaphysis junction of the femur or tibia. On radiographs, the fibrous cortical defects are eccentric cortically based lucent lesions with mineralized rim (**Figure 18A** and **B**). There is no involvement of the underlying medullary cavity. There is no periosteal reaction. The fibrous cortical defects are typically hypointense on T1 weighted images and hyperintense on T2-weighted images (**Figure 18C** and **D**). The signal intensity depends on the stage of healing. Fibrous cortical defects are typically seen incidentally on radiographs. These are no-touch lesions (no treatment is required). Benign fibro-osseous lesions may be metabolically active on FDG PET CT exam and should not be confused

*Fibrous cortical defect: Frontal (A) and lateral (B) radiographs of distal femur demonstrate eccentric lucent intracortical defect (white arrows) outlined by a rim of sclerosis. Note that there is no involvement of the underlying medullary cavity, and there is no periosteal reaction. The lesion (white arrows) demonstrates a hypointense T1 signal (C) and increased T2 signal with a peripheral hypointense sclerotic rim (D).*

*Juxtacortical chondroma: Frontal radiograph of the left tibia and fibula (A) demonstrates a well-defined distal tibial metadiaphyseal lucent lesion (white arrow) with underlying cortical saucerization or scalloping(yellow arrows) and subjacent cortical sclerosis. It demonstrates a hypointense T1 signal (B) and an increased T2 signal (C). T1-weighted fat-saturated pre (D) and postcontrast (E) images demonstrate peripheral enhancement of*

with metastases [61].

*Recent Advances in Bone Tumours and Osteoarthritis*

**Figure 18.**

**40**

**Figure 17.**

*the chondroma lesion (white arrow).*

2.**Nonossifying fibroma:** Nonossifying fibroma is a benign fibrous lesion composed of spindle cells in a collagenous matrix. Nonossifying fibroma is generally greater than 3 cm in greatest dimension (as opposed to a fibrous cortical defect less than 3 cm in diameter) [62]. Nonossifying fibroma typically originates in the metaphysis and is cortically based, most commonly found around the knee and distal tibia. It can be multifocal in 8% of cases. Multifocal nonossifying fibromas may be associated with neurofibromatosis (Jaffe-Campanacci syndrome). Nonossifying fibroma is usually asymptomatic; however, it could present with pathological fracture. It is typically seen in the first and second decade of life.

Radiographic and CT appearance depends on the morphologic age of the lesion. Initially, the lesion appears as a lytic, geographic area with a thin sclerotic margin (**Figure 19A** and **B**). During early filling phases, it has a thicker sclerotic margin forming peripheral bone. During late stages, the lesion may be entirely sclerotic with usual remodeling to normal bone type appearance. On MRI, the lesion is hypointense to skeletal muscle on T1 and heterogeneous on fluid sensitive sequences with low signal areas and hyperintense areas (**Figure 19C** and **D**). The regions of low signal areas are fibrous elements and hemosiderin. There is peripheral and septal enhancement following contrast administration. No cortical destruction or soft tissue mass lesion is demonstrated. No treatment is required in a vast majority of cases. If there is a risk for pathologic fracture due to the size of the lesion, curettage and bone grafting can be performed. Syndromic form of multiple nonossifying fibromas has a higher rate of recurrence after surgical removal [63].

3.**Fibrous Dysplasia**: Fibrous dysplasia (FD) is a developmental disorder characterized by the replacement of normal bone by immature bone and cartilaginous tissue. Most cases are sporadic and are related to a mutation in the GNAS1 gene. GNAS gene codes for the stimulatory alpha subunit of guanine nucleotide-binding protein, and its mutation result in persistent adenyl cyclase activation leading to osteoblastic proliferation. FD comprises

#### **Figure 19.**

*Non-Ossifying Fibroma: Frontal and lateral radiographs of femur demonstrate an eccentric cortically based radiolucent lesion with sclerotic margin in distal meta-diaphysis (A, B). On MRI of the same patient, the lesion demonstrates predominantly hypointense signal on T1 and heterogenous signal on STIR due to fibrous elements and hemosiderin (C, D).*

about 5–7% of all cases of benign tumors [64]. It can involve any bone and any part of the bone.

Four clinical presentations of FD have been described [65]:


Generally, FD lesions are lytic and well-defined but can look like almost anything and are not associated with soft tissue swelling. The radiographical features of FD can vary from ground-glass appearance, purely cystic (completely lucent) lesions, mixed cystic and sclerotic lesions, to sclerotic lesions. They may demonstrate a geographic (circumscribed) pattern with or without a sclerotic border or appear as expanded lesions with or without associated endosteal scalloping. CT accurately delineates margins of the FD lesions and helps in detecting subtle fractures [67]. FD lesions demonstrate different CT patterns depending upon the patient's age, varying from homogeneous dense lesions in the pre-pubertal life to a

mixed lucent-dense pattern between ages of 10–20 years, and some of these lesions may appear ground-glass in adult life. Diagnosing FD lesions purely by MRI is highly challenging because of the highly variable signal demonstrated by these lesions. Typically, the T1 signal is related to the ratio of fibrous tissue to the mineralized matrix, with the FD lesions with high fibrous component showing an intermediate T1 signal, compared to the low signal intensity of lesions with the highly mineralized matrix. The metabolically active fibrous component appears hyperintense on T2-weighted imaging and demonstrates intense enhancement because of high vascularity [68]. Franz et al. described the "milk cloud appearance" of the ground-glass FD lesions on contrast-enhanced T1-weighted MR imaging [69]. Active FD lesions demonstrate increased uptake on 18F-FDG PET/CT imaging (18F-NaF is a bone-seeking positron-emitting radiopharmaceutical) which is cur-

*McCune Albright syndrome: Radiographs (A–C) of the right humerus, left elbow and distal leg demonstrate extensive polyostotic fibrous dysplasia (white arrows) with associated deformities. Axial CT head bone algorithm image (D) demonstrates the characteristic ground-glass appearance of the cranium (yellow arrow) and diffuse widening of diploic space. Axial T2-weighted MR image (E) reveals a heterogenous mixed pattern of low and high SI within the expansile lesion. Also demonstrated is the heterogeneous T1 signal of the thickened*

In most cases, no treatment is required. Curettage and bone grafting is an option if there is a risk for pathologic fracture due to the size of the FD lesion. Persistent

**Langerhans cell histiocytosis (LCH)/Eosinophilic granuloma:** Langerhans cell

rently the imaging modality of choice to evaluate FD activity [70].

moderate-to-severe bone pain of FD can be controlled by intravenous

osteonecrosis of the jaw) [71].

**43**

**Figure 21.**

**3.1 Histiocytic/Langerhans cell lesions**

*calvarium (yellow arrow) in fibrous dysplasia (F).*

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

bisphosphonate therapy. However, it should be started only after ensuring the normocalcemic status of the patient and dental evaluation (to decrease the risk of

histiocytosis is neoplastic proliferation of Langerhans cells/histiocytes in the

#### **Figure 20.**

*Fibrous dysplasia: Left humerus radiograph (A) demonstrates an expansile diaphyseal lesion (white arrow) with a ground-glass matrix. The lesion (white arrows) demonstrates hypointense T1 signal (B), heterogeneous but predominantly increased T2 signal (C), and heterogeneous postcontrast enhancement (D).*

#### **Figure 21.**

about 5–7% of all cases of benign tumors [64]. It can involve any bone and any

1.Monostotic FD (70–80% of all FD): Single bone is involved (**Figure 20**) with craniofacial involvement in 10–27% of cases. It generally manifests at 10–30 years of age. FD lesions do not demonstrate an increase in size after

Craniofacial involvement is seen in 40–100% of cases. It usually manifests before age 10. Polyostotic FD lesions, in some cases, increase in size even after

3.McCune-Albright syndrome (3%): It is characterized by café-au-lait skin macules, polyostotic fibrous dysplasia, and endocrine hyperfunction disorders

(precocious puberty, pituitary adenomas secreting growth hormone,

4.Mazabraud syndrome: It is characterized by the coexistence of polyostotic

Generally, FD lesions are lytic and well-defined but can look like almost anything and are not associated with soft tissue swelling. The radiographical features of FD can vary from ground-glass appearance, purely cystic (completely lucent) lesions, mixed cystic and sclerotic lesions, to sclerotic lesions. They may demonstrate a geographic (circumscribed) pattern with or without a sclerotic border or appear as expanded lesions with or without associated endosteal scalloping. CT accurately delineates margins of the FD lesions and helps in detecting subtle fractures [67]. FD lesions demonstrate different CT patterns depending upon the patient's age, varying from homogeneous dense lesions in the pre-pubertal life to a

*Fibrous dysplasia: Left humerus radiograph (A) demonstrates an expansile diaphyseal lesion (white arrow) with a ground-glass matrix. The lesion (white arrows) demonstrates hypointense T1 signal (B), heterogeneous*

*but predominantly increased T2 signal (C), and heterogeneous postcontrast enhancement (D).*

fibrous dysplasia lesion and intramuscular myxomas.

hyperthyroidism, and autonomous adrenal hyperplasia). Increased growth and recurrence of the FD lesions are seen [66]. Some examples include the classic "Shepherd's crook" deformity of the femur, coxa vara, and scoliosis resulting

2.Polyostotic FD (20–25%): Multiple bones are affected (**Figure 21**).

Four clinical presentations of FD have been described [65]:

part of the bone.

*Recent Advances in Bone Tumours and Osteoarthritis*

puberty.

puberty.

from spinal FD.

**Figure 20.**

**42**

*McCune Albright syndrome: Radiographs (A–C) of the right humerus, left elbow and distal leg demonstrate extensive polyostotic fibrous dysplasia (white arrows) with associated deformities. Axial CT head bone algorithm image (D) demonstrates the characteristic ground-glass appearance of the cranium (yellow arrow) and diffuse widening of diploic space. Axial T2-weighted MR image (E) reveals a heterogenous mixed pattern of low and high SI within the expansile lesion. Also demonstrated is the heterogeneous T1 signal of the thickened calvarium (yellow arrow) in fibrous dysplasia (F).*

mixed lucent-dense pattern between ages of 10–20 years, and some of these lesions may appear ground-glass in adult life. Diagnosing FD lesions purely by MRI is highly challenging because of the highly variable signal demonstrated by these lesions. Typically, the T1 signal is related to the ratio of fibrous tissue to the mineralized matrix, with the FD lesions with high fibrous component showing an intermediate T1 signal, compared to the low signal intensity of lesions with the highly mineralized matrix. The metabolically active fibrous component appears hyperintense on T2-weighted imaging and demonstrates intense enhancement because of high vascularity [68]. Franz et al. described the "milk cloud appearance" of the ground-glass FD lesions on contrast-enhanced T1-weighted MR imaging [69].

Active FD lesions demonstrate increased uptake on 18F-FDG PET/CT imaging (18F-NaF is a bone-seeking positron-emitting radiopharmaceutical) which is currently the imaging modality of choice to evaluate FD activity [70].

In most cases, no treatment is required. Curettage and bone grafting is an option if there is a risk for pathologic fracture due to the size of the FD lesion. Persistent moderate-to-severe bone pain of FD can be controlled by intravenous bisphosphonate therapy. However, it should be started only after ensuring the normocalcemic status of the patient and dental evaluation (to decrease the risk of osteonecrosis of the jaw) [71].

#### **3.1 Histiocytic/Langerhans cell lesions**

**Langerhans cell histiocytosis (LCH)/Eosinophilic granuloma:** Langerhans cell histiocytosis is neoplastic proliferation of Langerhans cells/histiocytes in the

of cases occur between 20 and 50 years of age). It is rarely seen in the pediatric age group (3% of cases occur before age 14). Though GCT mainly involves long bones, any bone can be affected. The most common location of GCT is around the knee (distal femur and proximal tibia), followed by the distal radius and sacrum [74]. Campanacci and Enneking's clinic radiological staging of GCT: Stage I-The lesion is restricted to the marrow, and bone contour is not affected (cortex may be thinned out); Stage II- Cortical bulging without any signs of rupture; Stage III- Cortical

Typical radiographic presentation of GCT is that of a circumscribed, eccentric, epiphyseal lytic lesion that extends to the subchondral bone in patients with closed physis. GCT demonstrates a "soap bubble" appearance on radiographs and CT because of bony septae (**Figure 23A** and **B**). The MR features of GCT are

nonspecific. Most commonly, GCT shows hypointense T1 signal and heterogeneous T2 signal (due to collagen content of fibrous components of GCT and deposition of hemosiderin) [76] (**Figure 23C**–**F**). Contrast administration helps in delineating solid and cystic components. On scintigraphy, there is increased Technetium 99 m– methylene diphosphonate uptake along the periphery of the lesion with central photopenia. An aggressive GCT may demonstrate expansile remodeling, cortical thinning or destruction, a wide zone of transition, and associated soft tissue. Fluid– fluid levels within GCT suggest secondary aneurysmal bone cyst (ABC) formation. Though intralesional procedures (such as curettage and cement placement) are a preferred approach to treat GCT, they are complicated by recurrence because of residual tumor tissue. He et al. described marginal infiltration as the "paintbrush borders" sign on MRI and advocated it as an independent prognostic factor for local

recurrence of GCTB after intralesional curettage [77]. In advanced GCT, Denosumab is recommended for immediate local control and facilitates surgery

*Giant cell tumor: Frontal radiograph of the left ankle (A) demonstrates a circumscribed lytic lesion (white arrow) in the talus. Axial CT bone window image (B) better depicts the lobulated lytic lesion (white arrow) with scalloped margins. The lytic lesion (white arrow) demonstrates a heterogeneous hyperintense T2 signal (C). On the T1-weighted image (D), the lesion is isointense to muscle. Post-treatment MR images reveal dense*

*hypointense signal on both T1-weighted (E) and T2-weighted (F).*

breach with an invasion of soft tissues [75].

*Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

later [78].

**Figure 23.**

**45**

#### **Figure 22.**

*Eosinophilic granuloma: Skull radiograph (A) demonstrates a punched-out lucent lesion (white arrow) without a mineralized rim. Sagittal bone window image of the thoracic spine (B) reveals a collapsed vertebral body, namely "vertebra plana" (black arrow). Frontal radiograph of left tibia (C) showing an expansile welldefined osteolytic diaphyseal lesion (white arrow)with a benign periosteal reaction. Axial CT bone window image (D) at the level of the diaphyseal lesion demonstrates a punched-out lucent lesion (white arrow). MR images reveal intermediate T1 signal (E), heterogeneous increased T2 signal (F), and thick peripheral enhancement (F).*

reticuloendothelial system. These cells produce prostaglandins which are responsible for medullary bone resorption. The incidence of LCH is approximately 1 in 200 000 children [72]. Flat bones are most commonly involved in approximately 65–70% of cases. Skull is the most common site of involvement in flat bones. The monostotic form is more common, seen in approximately 70% of cases [73]. The mean age at diagnosis is typically 5–10 years. Classic radiographic/CT appearance includes solitary or multiple punched-out skull lesions without sclerotic rim (**Figure 22A**). There is a typical beveled edge appearance due to the asymmetrical involvement of inner and outer tables. Spinal lesions may present with vertebra plana (complete collapse and flattening of vertebral body) (**Figure 22B**). When present in long bones, the eosinophilic granuloma is a permeative aggressive appearing lesion with possible associated endosteal scalloping, periosteal reaction, and soft tissue mass (**Figure 22C** and **D**). The lesion may present in any part of bone but most commonly affects diaphysis. On MRI, these lesions are hypointense on T1, hyperintense on T2/STIR with diffuse postcontrast enhancement (**Figure 22E**–**G**). Whole-body PET/CT can be utilized to evaluate polyostotic disease and monitor for response to therapy. LCH commonly undergoes spontaneous resolution. If the symptoms persist, excision and curettage are the treatment of choice.

#### **3.2 Giant cell lesions**

**Giant cell tumor:** Giant cell tumor (GCT) of bone, a benign but locally aggressive tumor, comprises multinucleated giant cells interspersed with mononuclear stromal cells. It comprises 20% of all benign bone tumors and 5% of all primary bone tumors. GCT is more prevalent in females and between 20 and 30 years (80%

#### *Imaging of Pediatric Benign Bone Tumors DOI: http://dx.doi.org/10.5772/intechopen.99021*

of cases occur between 20 and 50 years of age). It is rarely seen in the pediatric age group (3% of cases occur before age 14). Though GCT mainly involves long bones, any bone can be affected. The most common location of GCT is around the knee (distal femur and proximal tibia), followed by the distal radius and sacrum [74].

Campanacci and Enneking's clinic radiological staging of GCT: Stage I-The lesion is restricted to the marrow, and bone contour is not affected (cortex may be thinned out); Stage II- Cortical bulging without any signs of rupture; Stage III- Cortical breach with an invasion of soft tissues [75].

Typical radiographic presentation of GCT is that of a circumscribed, eccentric, epiphyseal lytic lesion that extends to the subchondral bone in patients with closed physis. GCT demonstrates a "soap bubble" appearance on radiographs and CT because of bony septae (**Figure 23A** and **B**). The MR features of GCT are nonspecific. Most commonly, GCT shows hypointense T1 signal and heterogeneous T2 signal (due to collagen content of fibrous components of GCT and deposition of hemosiderin) [76] (**Figure 23C**–**F**). Contrast administration helps in delineating solid and cystic components. On scintigraphy, there is increased Technetium 99 m– methylene diphosphonate uptake along the periphery of the lesion with central photopenia. An aggressive GCT may demonstrate expansile remodeling, cortical thinning or destruction, a wide zone of transition, and associated soft tissue. Fluid– fluid levels within GCT suggest secondary aneurysmal bone cyst (ABC) formation.

Though intralesional procedures (such as curettage and cement placement) are a preferred approach to treat GCT, they are complicated by recurrence because of residual tumor tissue. He et al. described marginal infiltration as the "paintbrush borders" sign on MRI and advocated it as an independent prognostic factor for local recurrence of GCTB after intralesional curettage [77]. In advanced GCT, Denosumab is recommended for immediate local control and facilitates surgery later [78].

#### **Figure 23.**

reticuloendothelial system. These cells produce prostaglandins which are responsible for medullary bone resorption. The incidence of LCH is approximately 1 in 200 000 children [72]. Flat bones are most commonly involved in approximately 65–70% of cases. Skull is the most common site of involvement in flat bones. The monostotic form is more common, seen in approximately 70% of cases [73]. The mean age at diagnosis is typically 5–10 years. Classic radiographic/CT appearance includes solitary or multiple punched-out skull lesions without sclerotic rim (**Figure 22A**). There is a typical beveled edge appearance due to the asymmetrical involvement of inner and outer tables. Spinal lesions may present with vertebra plana (complete collapse and flattening of vertebral body) (**Figure 22B**). When present in long bones, the eosinophilic granuloma is a permeative aggressive appearing lesion with possible associated endosteal scalloping, periosteal reaction, and soft tissue mass (**Figure 22C** and **D**). The lesion may present in any part of bone but most commonly affects diaphysis. On MRI, these lesions are hypointense on T1, hyperintense on T2/STIR with diffuse postcontrast enhancement (**Figure 22E**–**G**). Whole-body PET/CT can be utilized to evaluate polyostotic disease and monitor for response to therapy. LCH commonly undergoes spontaneous resolution. If the symptoms persist, excision and curettage

*Eosinophilic granuloma: Skull radiograph (A) demonstrates a punched-out lucent lesion (white arrow) without a mineralized rim. Sagittal bone window image of the thoracic spine (B) reveals a collapsed vertebral body, namely "vertebra plana" (black arrow). Frontal radiograph of left tibia (C) showing an expansile welldefined osteolytic diaphyseal lesion (white arrow)with a benign periosteal reaction. Axial CT bone window image (D) at the level of the diaphyseal lesion demonstrates a punched-out lucent lesion (white arrow). MR images reveal intermediate T1 signal (E), heterogeneous increased T2 signal (F), and thick peripheral*

*Recent Advances in Bone Tumours and Osteoarthritis*

**Giant cell tumor:** Giant cell tumor (GCT) of bone, a benign but locally aggressive tumor, comprises multinucleated giant cells interspersed with mononuclear stromal cells. It comprises 20% of all benign bone tumors and 5% of all primary bone tumors. GCT is more prevalent in females and between 20 and 30 years (80%

are the treatment of choice.

**3.2 Giant cell lesions**

**44**

**Figure 22.**

*enhancement (F).*

*Giant cell tumor: Frontal radiograph of the left ankle (A) demonstrates a circumscribed lytic lesion (white arrow) in the talus. Axial CT bone window image (B) better depicts the lobulated lytic lesion (white arrow) with scalloped margins. The lytic lesion (white arrow) demonstrates a heterogeneous hyperintense T2 signal (C). On the T1-weighted image (D), the lesion is isointense to muscle. Post-treatment MR images reveal dense hypointense signal on both T1-weighted (E) and T2-weighted (F).*
