**6. Diagnosis**

Chordoma and chondrosarcoma have a common overview and similar anatomic location, and can be troublesome to recognize some time before the histopathologic and immunohistochemical examination; in any case, tumors have a distinctive origin and distinctive prognosis. Chondroid chordomas, in spite of having a few pathologic characteristics that are comparable to chondrosarcoma, carry on clinically like chordomas. The preoperative separation between chordomas and chondrosarcomas based on the clinical presentation and clinical and instrument-based diagnostics alone is very tough.

Intracranial chordomas usually have a midline cranium base area whereas most chondrosarcomas emerge along the petro-occipital fissure. On the other hand, chondrosarcomas may sometimes have a midline area, making it difficult to differentiate between chondrosarcoma and an intracranial chordoma. In addition, these two tumors have alike signal intensity on T1- and T2-weighted magnetic resonance images. Hence, direct, globular, or arc-like calcifications when present in chondrosarcomas may help to distinguish them from intracranial chordomas [20].

Plasmacytoma and lymphoma sometimes include the cranium base and cause damage to lytic bone. Craniopharyngiomas, other than illustrating a generally characteristic signal intensity, are found more anteriorly in midline than are intracranial chordomas. Other differentials, though uncommon, may include aggressive pituitary adenoma, histiocytosis X, trigeminal neuroma, dermoid and epidermoid cyst.

Neurosurgical methods frequently utilized for the resection of intracranial chordomas and chondrosarcomas are trans-sphenoidal, Cranio-orbito-zygomatic, transbasal, transcondylar, transzygomatic amplified center fossa, and transmaxillary methodologies. Chordomas and chondrosarcomas are not sensitive to chemotherapy and thus the management modality might be a combination of surgical resection with a maximal extraction and adjuvant radiotherapy for both chondrosarcomas and chordomas.

Differential diagnosis includes mainly metastatic carcinoma, chondrosarcoma, and myxopapillary ependymoma. Metastatic carcinoma and chordomas both show positive responses with epithelial markers. It is unusual for metastatic carcinoma to have the lobulated growth pattern of chordoma whereas chondrosarcoma may grow in a lobulated pattern but without fibrous septa. Myxopapillary ependymoma is easy to differentiate from chordoma as they do not stain for epithelial markers [21]. In electron, microscopic view chordoma shows desmosome and mitochondrial rough endoplasmic reticulum complex whereas both are absent in case of chondrosarcoma [22].

### **6.1 Radiology**

Cranium base chordomas are ordinarily found within the midline [18] and appear to start within the bone, penetrating the way of slightest resistance and inevitably creating a soft tissue mass. In spite of the fact that their clinical and imaging presentations are analogous, they infer from distinctive roots. CT and MRI, both are required for accurate characterization of clival chordomas and their association to adjacent anatomy (**Figures 2** and **3**). Currently, MRI is the most suitable for the radiologic evaluation of intracranial chordomas [23].

Chowhan and his colleagues (2012) studied through MRI of chondrosarcoma and showed a T2 hyperintense lesion involving the clivus, petrous temporal bone, and sphenoid bone [4]. This lesion was hypointense on a T1-weighted image (**Figure 4a**) and enhanced heterogeneously in the postcontrast (gadolinium) study (**Figure 4b**).

#### **Figure 2.**

**MRI:** *Expansile lobulated lytic lesion in clivus which is hyperintense on T2 images (a, b) hypointense on T1 (c) image showing heterogeneous enhancement after contrast administration (d) extending into cisterns causing compression over brainstem and displacing basilar artery, lesion is extending into sella (red arrow).*

#### **Figure 3.**

*Figure (a) axial CT brain window and figure (b) axial CT bone window showing subtle lesion on brain window and small lytic lesion on bone window images in a 48-year-old female.MRI images of the same patient 1 year later show the lesion have grown and appear as T2 hyperintense lesion (c), T1 hypointense lesion (d, e) which shows heterogeneous enhancement after contrast administration (f).*

#### **Figure 4.**

*Chondrosarcoma: (a) Postcontrast T1-weighted axial image shows heterogeneous enrichment of lesion. (b) Figure showing T1-weighted axial image: Lesion is hypointense on this image.*

CT and MRI are essential to decide the tumor localization, as well as the degree of tumor development and the treatment logic, is to maximize tumor resection with reduced morbidity. On susceptibility-weighted imaging the chordoma show multiple areas of blooming which is a nonspecific finding and diffusion-weighted

imaging can help to differentiate the conventional vs. dedifferentiated based on cut-off values of apparent diffusion coefficient.
