**1. Introduction**

Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up to 18% in adult population [1]. The incidence is higher in females older than 50 years.

Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and

other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up

manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts.

to 18% in adult population [1]. The incidence is higher in females older than 50 years.

#### **2. Classification and etiology** manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for **1. Definition** Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and

#### **2.1. Serous/simple hepatic cyst** to 18% in adult population [1]. The incidence is higher in females older than 50 years. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up

staining ×400.

staining ×400.

**1. Definition**

Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid [2]. Microscopically, they are lined by a single layer of cuboid, columnar, flattened (Figure 1) or pseudostratified (Figure 2), or by stratified epithelial cells (Figure 3), resembling biliary epithelial cells. **2. Classification and etiology** *2.1. Serous/simple hepatic cyst* Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid [2]. Microscopically, they are lined by a single layer of cuboid, columnar, flattened (Figure 1) or pseudostratified (Figure 2), or by stratified epithelial cells (Figure 3), resembling biliary epithelial cells. **2. Classification and etiology** *2.1. Serous/simple hepatic cyst* Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid

staining ×400. **Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin staining ×400. **Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin staining ×400.

A B

**Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

**Figure 2.** Serous cyst with pseudostratified epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin staining ×400.

**Figure 2.** Serous cyst with pseudostratified epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

2

2

**Figure 3.** Serous simple cyst with stratified cuboidal epithelium. Hematoxylin and eosin staining ×200.

### **2.2. Polycystic liver disease**

**1. Introduction**

250 Recent Advances in Liver Diseases and Surgery

than 50 years.

**2. Classification and etiology**

*2.1. Serous/simple hepatic cyst*

staining ×400.

staining ×400.

staining ×400.

eosin staining ×400.

staining ×400.

staining ×400.

**2. Classification and etiology**

**2. Classification and etiology** *2.1. Serous/simple hepatic cyst*

**2.1. Serous/simple hepatic cyst**

**1. Definition**

**1. Definition**

Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up to 18% in adult population [1]. The incidence is higher in females older

Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid [2]. Microscopically, they are lined by a single layer of cuboid, columnar, flattened (Figure 1) or pseudostratified (Figure 2), or by

Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid [2]. Microscopically, they are lined by a single layer of cuboid, columnar, flattened (Figure 1) or pseudostratified (Figure

Hepatic serous or simple cysts may be single or multiple and are considered to be congenital. They are derived from aberrant bile ducts that have apparently lost communication with the biliary tree and continue to secrete intramural fluid [2]. Microscopically, they are lined by a single layer of cuboid, columnar, flattened (Figure 1) or pseudostratified (Figure

**Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

**Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

**Figure 1.** Serous cyst with flattened epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

A B

A B

A B

A B

Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up

Nonparasitic hepatic cysts encompass a heterogeneous group of disorders, which differ in etiology, prevalence, and manifestations. The term hepatic cyst usually refers to solitary nonparasitic cysts of the liver, also known as simple cysts. Generally, hepatic cysts are incidentally found during surgery and more frequently during imaging examinations for other reasons. Nowadays, due to the imaging procedures, prevalence of nonparasitic hepatic cysts is found increased up

2

2

**Figure 2.** Serous cyst with pseudostratified epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

**Figure 2.** Serous cyst with pseudostratified epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and eosin

**Figure 2.** Serous cyst with pseudostratified epithelium. (A) Hematoxylin and eosin staining ×100. (B) Hematoxylin and

stratified epithelial cells (Figure 3), resembling biliary epithelial cells.

2), or by stratified epithelial cells (Figure 3), resembling biliary epithelial cells.

2), or by stratified epithelial cells (Figure 3), resembling biliary epithelial cells.

to 18% in adult population [1]. The incidence is higher in females older than 50 years.

to 18% in adult population [1]. The incidence is higher in females older than 50 years.

Serous hepatic cysts are also linked to genetic disorders such as polycystic liver disease (PLD) with/without autosomal dominant polycystic kidney disease (ADPKD) or Caroli disease. Isolated PLD is associated with heterozygous mutations in PRKCSH or SEC63 genes. PLD associated with ADPKD is linked with mutations in the PKD1 or PKD2 gene [3]. Overall prevalence is similar for both genders, but females develop a more severe liver disease. Pregnancy, multiparity, and use of steroids increase the risk for severe hepatic cystic disease.

Gigot and collaborators have described a classification for patients with polycystic liver disease based on the number and size of hepatic cysts and residual normal liver parenchyma between the cysts. This description is based on preoperative computed tomography (CT) [4]. Also, this classification can delineate the therapeutic strategy [5].


It is of exquisite importance to differentiate hepatic cyst from hydatid hepatic cyst, hepatic cystadenoma, and hepatic cystadenocarcinoma before proceeding with the treatment. In certain situations, it can be very challenging to properly diagnose a hepatic cystic mass [6, 7]. There are also rare hepatic cystic lesions that must be taken into consideration [8]. In pediatric population, the surgeon should be aware of the wide range of other types of liver cysts to ensure appropriate treatment [9].

#### **2.3. Localized Caroli disease or solitary dilatation of intrahepatic biliary duct**

Caroli disease is an autosomal recessive inheritance linked to mutation in PKHD1 gene. It is classified as type V choledochal cyst by the Todani classification [10]. The cystic lesions are of noncystic parenchyma

of noncystic parenchyma

depicted as irregular in shape, fusiform, or saccular (Figures 4A). On MRCP they are seen to communicate with biliary tree (Figure 4B). On gross examination of the operative specimen, the cystic cavity contains biliary sludge and even gallstones (Figure 5). Caroli disease is an autosomal recessive inheritance linked to mutation in PKHD1 gene. It is classified as type V choledochal cyst by the Todani classification [10]. The cystic lesions are depicted as irregular in shape, fusiform, or saccular (Figures 4A). On MRCP they are seen to communicate with biliary tree (Figure 4B). On gross examination of the In pediatric population, the surgeon should be aware of the wide range of other types of liver cysts to ensure appropriate treatment [9].

cystadenocarcinoma before proceeding with the treatment. In certain situations, it can be very challenging to properly diagnose a hepatic cystic mass [6, 7]. There are also rare hepatic cystic lesions that must be taken into consideration [8].

operative specimen, the cystic cavity contains biliary sludge and even gallstones (Figure 5).

*2.3. Localized Caroli disease or solitary dilatation of intrahepatic biliary duct*

Type I—less than 10 large cyst (7–10 cm) with large areas of noncystic parenchyma

and only a few areas of normal liver parenchyma between cysts [2, 4, 5]

*2.3. Localized Caroli disease or solitary dilatation of intrahepatic biliary duct*

Type I—less than 10 large cyst (7–10 cm) with large areas of noncystic parenchyma

Type II—diffuse involvement of liver parenchyma by medium‐sized cysts (5–7 cm) with remaining large areas

Type III—massive, diffuse involvement of liver parenchyma by small‐ and medium‐sized cysts (less than 5 cm)

and only a few areas of normal liver parenchyma between cysts [2, 4, 5]

Type II—diffuse involvement of liver parenchyma by medium‐sized cysts (5–7 cm) with remaining large areas

Type III—massive, diffuse involvement of liver parenchyma by small‐ and medium‐sized cysts (less than 5 cm)

**Figure 4.** Localized Caroli disease. (A) MRI, axial section: group of cysts in hepatic segment VIII. (B) MRCP, coronal section: group of cysts that communicate with biliary

tree.

It is of exquisite importance to differentiate hepatic cyst from hydatid hepatic cyst, hepatic cystadenoma, and hepatic cystadenocarcinoma before proceeding with the treatment. In certain situations, it can be very challenging to properly diagnose a hepatic cystic mass [6, 7]. There are also rare hepatic cystic lesions that must be taken into consideration [8]. In pediatric population, the surgeon should be aware of the wide range of other types of liver cysts to ensure appropriate

**Figure 4.** Localized Caroli disease. (A) MRI, axial section: group of cysts in hepatic segment VIII. (B) MRCP, coronal section: group of cysts that communicate with biliary tree. communicate with biliary tree.

Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fails to observe the biliary **Figure 5.** Localized Caroli disease. (A) Resected specimen with biliary cysts filled with bile sludge. (B) Histological examination with hematoxylin and eosin staining ×100. **Figure 5.** Localized Caroli disease. (A) Resected specimen with biliary cysts filled with bile sludge. (B) Histological ex‐ amination with hematoxylin and eosin staining ×100.

papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the

#### communication between the cystic lesion and the bile duct [11]. *2.4. Intrahepatic biliary papilloma*  **2.4. Intrahepatic biliary papilloma**

septa may show calcifications.

*2.5. Biliary cystadenoma and cystadenocarcinoma* Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle‐aged woman. The exact etiology of this insidiously progressive tumor is unknown. These cysts may originate from a congenitally aberrant bile duct or directly from a primitive hepatobiliary stem cell. Cystadenoma of the liver is characterized by multilocular cysts with internal septation and epithelial lining composed of Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fails to observe the biliary papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the communication between the cystic lesion and the bile duct [11]. *2.5. Biliary cystadenoma and cystadenocarcinoma* Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fail to observe the biliary papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the communication between the cystic lesion and the bile duct [11].

#### columnar to cuboidal cells capable of mucin production. They usually contain clear mucinous fluid and rarely the fluid may be bilious, purulent, proteinaceous, or hemorrhagic. Bloody fluid often signifies a malignant component [12]. The Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle‐aged woman. The exact etiology **2.5. Biliary cystadenoma and cystadenocarcinoma**

3 septa may show calcifications. of this insidiously progressive tumor is unknown. These cysts may originate from a congenitally aberrant bile duct or directly from a primitive hepatobiliary stem cell. Cystadenoma of the liver is characterized by multilocular cysts with internal septation and epithelial lining composed of columnar to cuboidal cells capable of mucin production. They usually contain clear mucinous fluid and rarely the fluid may be bilious, purulent, proteinaceous, or hemorrhagic. Bloody fluid often signifies a malignant component [12]. The Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle-aged woman. The exact etiology of this insidiously progressive tumor is unknown. This cyst may originate from a congenitally aberrant bile duct or directly from a primitive hepatobiliary stem cell.

3

Cystadenoma of the liver is characterized by multilocular cysts with internal septation and epithelial lining composed of columnar to cuboidal cells capable of mucin production. They usually contain clear mucinous fluid and rarely the fluid may be bilious, purulent, proteina‐ ceous, or hemorrhagic. Bloody fluid often signifies a malignant component [12]. The septa may show calcifications.

depicted as irregular in shape, fusiform, or saccular (Figures 4A). On MRCP they are seen to communicate with biliary tree (Figure 4B). On gross examination of the operative specimen,

It is of exquisite importance to differentiate hepatic cyst from hydatid hepatic cyst, hepatic cystadenoma, and hepatic cystadenocarcinoma before proceeding with the treatment. In certain situations, it can be very challenging to properly diagnose a hepatic cystic mass [6, 7]. There are also rare hepatic cystic lesions that must be taken into consideration [8]. In pediatric population, the surgeon should be aware of the wide range of other types of liver cysts to ensure appropriate

operative specimen, the cystic cavity contains biliary sludge and even gallstones (Figure 5).

Caroli disease is an autosomal recessive inheritance linked to mutation in PKHD1 gene. It is classified as type V choledochal cyst by the Todani classification [10]. The cystic lesions are depicted as irregular in shape, fusiform, or saccular (Figures 4A). On MRCP they are seen to communicate with biliary tree (Figure 4B). On gross examination of the

**Figure 4.** Localized Caroli disease. (A) MRI, axial section: group of cysts in hepatic segment VIII. (B) MRCP, coronal

**Figure 5.** Localized Caroli disease. (A) Resected specimen with biliary cysts filled with bile sludge. (B) Histological examination with hematoxylin and eosin staining ×100.

**Figure 5.** Localized Caroli disease. (A) Resected specimen with biliary cysts filled with bile sludge. (B) Histological ex‐

Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fails to observe the biliary papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the

Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fail to observe the biliary papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the communication between the cystic lesion

Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle‐aged woman. The exact etiology of this insidiously progressive tumor is unknown. These cysts may originate from a congenitally aberrant bile duct or

Cystadenoma of the liver is characterized by multilocular cysts with internal septation and epithelial lining composed of columnar to cuboidal cells capable of mucin production. They usually contain clear mucinous fluid and rarely the fluid may be bilious, purulent, proteinaceous, or hemorrhagic. Bloody fluid often signifies a malignant component [12]. The

Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle-aged woman. The exact etiology of this insidiously progressive tumor is unknown. This cyst may originate from a congenitally aberrant bile duct or directly from a primitive hepatobiliary stem

*2.3. Localized Caroli disease or solitary dilatation of intrahepatic biliary duct*

Type I—less than 10 large cyst (7–10 cm) with large areas of noncystic parenchyma

Type II—diffuse involvement of liver parenchyma by medium‐sized cysts (5–7 cm) with remaining large areas

Type III—massive, diffuse involvement of liver parenchyma by small‐ and medium‐sized cysts (less than 5 cm)

and only a few areas of normal liver parenchyma between cysts [2, 4, 5]

Type II—diffuse involvement of liver parenchyma by medium‐sized cysts (5–7 cm) with remaining large areas

Type III—massive, diffuse involvement of liver parenchyma by small‐ and medium‐sized cysts (less than 5 cm)

It is of exquisite importance to differentiate hepatic cyst from hydatid hepatic cyst, hepatic cystadenoma, and hepatic cystadenocarcinoma before proceeding with the treatment. In certain situations, it can be very challenging to properly diagnose a hepatic cystic mass [6, 7]. There are also rare hepatic cystic lesions that must be taken into consideration [8]. In pediatric population, the surgeon should be aware of the wide range of other types of liver cysts to ensure appropriate

Caroli disease is an autosomal recessive inheritance linked to mutation in PKHD1 gene. It is classified as type V choledochal cyst by the Todani classification [10]. The cystic lesions are depicted as irregular in shape, fusiform, or saccular (Figures 4A). On MRCP they are seen to communicate with biliary tree (Figure 4B). On gross examination of the

> **Figure 4.** Localized Caroli disease. (A) MRI, axial section: group of cysts in hepatic segment VIII. (B) MRCP, coronal section: group of cysts that communicate with biliary

tree.

**Figure 4.** Localized Caroli disease. (A) MRI, axial section: group of cysts in hepatic segment VIII. (B) MRCP, coronal section: group of cysts that communicate with biliary

3

3

**Figure 5.** Localized Caroli disease. (A) Resected specimen with biliary cysts filled with bile sludge. (B) Histological examination with hematoxylin and eosin staining ×100.

A B

tree.

Biliary papilloma represents a tumorous growth of the bile duct epithelia in the bile duct lumen and can cause a localized dilatation of the intrahepatic bile duct. If native and contrast enhanced CT fails to observe the biliary papilloma, the bile duct dilatation may be confused with a hepatic serous cyst. ERCP can demonstrate the

A B

Biliary cystadenoma is a very rare cystic lesion of the liver that usually occurs in middle‐aged woman. The exact etiology of this insidiously progressive tumor is unknown. These cysts may originate from a congenitally aberrant bile duct or

Cystadenoma of the liver is characterized by multilocular cysts with internal septation and epithelial lining composed of columnar to cuboidal cells capable of mucin production. They usually contain clear mucinous fluid and rarely the fluid may be bilious, purulent, proteinaceous, or hemorrhagic. Bloody fluid often signifies a malignant component [12]. The

the cystic cavity contains biliary sludge and even gallstones (Figure 5).

operative specimen, the cystic cavity contains biliary sludge and even gallstones (Figure 5).

*2.3. Localized Caroli disease or solitary dilatation of intrahepatic biliary duct*

Type I—less than 10 large cyst (7–10 cm) with large areas of noncystic parenchyma

and only a few areas of normal liver parenchyma between cysts [2, 4, 5]

of noncystic parenchyma

*2.4. Intrahepatic biliary papilloma* 

amination with hematoxylin and eosin staining ×100.

**2.4. Intrahepatic biliary papilloma**

*2.4. Intrahepatic biliary papilloma* 

section: group of cysts that communicate with biliary tree.

communication between the cystic lesion and the bile duct [11].

*2.5. Biliary cystadenoma and cystadenocarcinoma*

directly from a primitive hepatobiliary stem cell.

**2.5. Biliary cystadenoma and cystadenocarcinoma**

septa may show calcifications.

*2.5. Biliary cystadenoma and cystadenocarcinoma*

and the bile duct [11].

directly from a primitive hepatobiliary stem cell.

septa may show calcifications.

cell.

communication between the cystic lesion and the bile duct [11].

treatment [9].

252 Recent Advances in Liver Diseases and Surgery

treatment [9].

of noncystic parenchyma

Two subgroups are distinguished by presence or absence of mesenchymal (ovarian like) stroma between an inner epithelial lining and an outer layer of collagenized connective tissue (Figure 6).

**Figure 6.** Cystadenoma without mesenchymal stroma. Hematoxylin and eosin staining ×200.

The mesenchymal stroma resembles primitive mesenchyme, and cell differentiation varies from smooth muscle or fibroblasts to adipocytes or capillaries. Cystadenoma with mesenchy‐ mal stroma occurs exclusively in women (Figure 7) possibly as a consequence of the female milieu influence, while cystadenoma without mesenchymal stroma predominates in men [13].

Mesenchymal stroma may give rise to both cystadenocarcinoma and sarcomas. Intrahepat‐ ic biliary cystadenoma cannot be clearly differentiated from cystadenocarcinoma before operation. Some authors consider the diagnostic value of the analysis of serum and aspirated cyst fluid for tumor markers. However, elevated carbohydrate antigen CA 19-9 and carcinoembryonic antigen CEA has been associated both with cystadenoma and cystadenocarcinoma [14]. Only histopathologic exam can certainly differentiate it from malignant degeneration. Being considered a premalignant lesion, surgical excision seems to be a wise decision in patients with intrahepatic biliary cystadenoma. If not completely resected, the recurrence in biliary cystadenoma is greater than 90% [12]. Moreover, if malignancy is not recognized, a simple fenestration may prove catastrophic to patient. Patients with cystadenocarcinoma with mesenchymal stroma have a good prognosis, whereas cystadenocarcinoma in men, which is not associated with mesenchymal stroma, has a worse prognosis, even after complete excision [15].

predominates in men [13].

**Figure 6.** Cystadenoma without mesenchymal stroma. Hematoxylin and eosin staining ×200.

The mesenchymal stroma resembles primitive mesenchyme, and cell differentiation varies from smooth muscle or

possibly as a consequence of the female milieu influence, while cystadenoma without mesenchymal stroma

4 **Figure 7.** Cystadenoma with mesenchymal stroma. (A) Hematoxylin and eosin staining ×200. (B) Hematoxylin and eo‐ sin staining ×400. (C) Immunohistochemical staining CK7 ×200. Cyst epithelium is positive for CK7. (D) Immunohisto‐ chemical staining CK8-18 ×200. Cyst epithelium is positive for CK8-18. (E) Immunohistochemical staining ER ×400. Mesenchymal stroma contains cells (brown cells) that are positively stained for estrogen receptors. (F) Immunohisto‐ chemical staining PgR ×400. Mesenchymal stroma contains cells (brown cells) that are positively stained for progester‐ one receptors.

#### **2.6. Bile duct hamartoma**

Bile duct hamartomas, also called von Meyenburg complexes, originate from embryonic bile ducts that fail to involute. Generally, they are encountered as an incidental finding at imaging, laparotomy, or autopsy. Macroscopically, they are cyst-like, grayish-white nodular lesions of 0.1-1.5 cm diameter that do not communicate with the biliary tree. Sometimes they are associated with Caroli's disease, PLD and congenital fibrosis. In case of intraoperative discovery, they may be misdiagnosed as liver metastases.

#### **2.7. Ciliated hepatic foregut cyst**

Ciliated hepatic foregut cysts are rare foregut developmental malformation usually solitary and unilocular. Generally, these are situated in the central segments of the liver (Figure 8). These cysts are characterized by the typical microscopic finding of four layers (the inner ciliated, pseudostratified, columnar epithelium; subepithelial connective tissue; smooth muscle layer; and an outer fibrous layer at microscopic examination). Squamous metaplasia may be present with potential transformation into squamous cell carcinoma. Malignant transformation to squamous cell carcinoma with aggressive behavior has been reported in 3% of adult cases [4, 16].

**Figure 8.** CT series showing a hepatic cyst situated in segment VIII, with an extension that is traced on the hepatic surface, raising the question of ciliated hepatic foregut cyst in a 14-year-old girl. The patient was submitted to open surgery due to the close proximity with the inferior vena cava and hepatic vein.

#### **2.8. Intrahepatic pancreatic pseudocyst**

**2.6. Bile duct hamartoma**

one receptors.

Bile duct hamartomas, also called von Meyenburg complexes, originate from embryonic bile ducts that fail to involute. Generally, they are encountered as an incidental finding at imaging, laparotomy, or autopsy. Macroscopically, they are cyst-like, grayish-white nodular lesions of 0.1-1.5 cm diameter that do not communicate with the biliary tree. Sometimes they are

4

**Figure 7.** Cystadenoma with mesenchymal stroma. (A) Hematoxylin and eosin staining ×200. (B) Hematoxylin and eo‐ sin staining ×400. (C) Immunohistochemical staining CK7 ×200. Cyst epithelium is positive for CK7. (D) Immunohisto‐ chemical staining CK8-18 ×200. Cyst epithelium is positive for CK8-18. (E) Immunohistochemical staining ER ×400. Mesenchymal stroma contains cells (brown cells) that are positively stained for estrogen receptors. (F) Immunohisto‐ chemical staining PgR ×400. Mesenchymal stroma contains cells (brown cells) that are positively stained for progester‐

**Figure 6.** Cystadenoma without mesenchymal stroma. Hematoxylin and eosin staining ×200.

predominates in men [13].

254 Recent Advances in Liver Diseases and Surgery

The mesenchymal stroma resembles primitive mesenchyme, and cell differentiation varies from smooth muscle or fibroblasts to adipocytes or capillaries. Cystadenoma with mesenchymal stroma occurs exclusively in women (Figure 7) possibly as a consequence of the female milieu influence, while cystadenoma without mesenchymal stroma

A B

C D

E F

Hepatic pseudocyst secondary to acute pancreatitis is extremely rare and is generally situated in the left lobe. A high level of amylase in the aspirated fluid confirms the diagnosis. Asymp‐ tomatic intrahepatic pseudocyst can be treated conservatively, and symptomatic intrahepatic pseudocyst can be managed either percutaneously or surgically [17].

#### **2.9. Posttraumatic hepatic cyst**

Only those symptomatic or of uncertain nature need treatment.

#### **2.10. Biloma**

Biloma appears as a cystic mass. It is caused by spontaneous, traumatic, or iatrogenic rupture of the biliary system.

#### **2.11. Peribiliary cysts**

Peribiliary cysts are mostly encountered in cirrhotic patients with portal hypertension or after liver transplantation. The cysts are located along the portal pedicles. Usually they are small and asymptomatic.

#### **2.12. Liver hematoma**

Liver hematomas are cystic lesions that develop after trauma, liver biopsy, or surgery.

#### **2.13. Hepatic epidermoid cyst**

Liver epidermoid cysts are extremely rare. These malformations have been diagnosed in pediatric patients, with the youngest one being 5 months years old. The importance of resection of such cystic lesions in pediatric population resides in the need of elimination of a lesion lined by squamous epithelium with possible squamous metaplasia that can potentially undergo malignant transformation, resulting in squamous cell carcinoma.

#### **2.14. Postcholecystectomy hepatic cystic mass**

The term of gossypiboma derived from the Latin term gossypium is used to define a forgotten surgical material in the body after surgery. Sometimes gossypiboma has a cyst-like appearance on imaging tests.

#### **2.15. Hepatic endometriosis**

So far only 22 cases of hepatic endometrioma have been reported in the literature [18]. Hepatic endometriosis should be considered in women of any age presenting with a hepatic cystic mass, with or without previous endometriosis history. Frozen sections of intraoperative transhepatic biopsy are necessary to avoid radical hepatectomy in order to decrease postop‐ erative morbidity and mortality. However, the diagnosis is confirmed through histological immunostaining. Complete pericystectomy is necessary to avoid recurrence.

#### **2.16. Hepatic vascular tumors**

Complete pericystectomy is necessary to avoid recurrence.

*2.15. Hepatic endometriosis*

There are hepatic vascular tumors with predominantly solid appearance at gross examination but with cyst-like appearance on imaging examinations due to the high water content. Histopathological diagnosis must differentiate between lymphangioma, hemangioma, hemangiopericytoma, or undifferentiated embryonal sarcoma (Figure 9). *2.16. Hepatic vascular tumors* There are hepatic vascular tumors with predominantly solid appearance at gross examination but with cyst‐like appearance on imaging examinations due to the high water content. Histopathological diagnosis must differentiate between lymphangioma, hemangioma, hemangiopericytoma, or undifferentiated embryonal sarcoma (Figure 9).

So far only 22 cases of hepatic endometrioma have been reported in the literature [18]. Hepatic endometriosis should be

#### **2.17. Liver metastases** *2.17. Liver metastases*

tomatic intrahepatic pseudocyst can be treated conservatively, and symptomatic intrahepatic

Biloma appears as a cystic mass. It is caused by spontaneous, traumatic, or iatrogenic rupture

Peribiliary cysts are mostly encountered in cirrhotic patients with portal hypertension or after liver transplantation. The cysts are located along the portal pedicles. Usually they are small

Liver hematomas are cystic lesions that develop after trauma, liver biopsy, or surgery.

Liver epidermoid cysts are extremely rare. These malformations have been diagnosed in pediatric patients, with the youngest one being 5 months years old. The importance of resection of such cystic lesions in pediatric population resides in the need of elimination of a lesion lined by squamous epithelium with possible squamous metaplasia that can potentially undergo

The term of gossypiboma derived from the Latin term gossypium is used to define a forgotten surgical material in the body after surgery. Sometimes gossypiboma has a cyst-like appearance

So far only 22 cases of hepatic endometrioma have been reported in the literature [18]. Hepatic endometriosis should be considered in women of any age presenting with a hepatic cystic mass, with or without previous endometriosis history. Frozen sections of intraoperative transhepatic biopsy are necessary to avoid radical hepatectomy in order to decrease postop‐ erative morbidity and mortality. However, the diagnosis is confirmed through histological

immunostaining. Complete pericystectomy is necessary to avoid recurrence.

pseudocyst can be managed either percutaneously or surgically [17].

Only those symptomatic or of uncertain nature need treatment.

malignant transformation, resulting in squamous cell carcinoma.

**2.14. Postcholecystectomy hepatic cystic mass**

**2.9. Posttraumatic hepatic cyst**

256 Recent Advances in Liver Diseases and Surgery

**2.10. Biloma**

of the biliary system.

**2.11. Peribiliary cysts**

and asymptomatic.

on imaging tests.

**2.15. Hepatic endometriosis**

**2.12. Liver hematoma**

**2.13. Hepatic epidermoid cyst**

Liver metastases from ovarian, pancreatic, colon, renal, or neuroendocrine cancer may have cyst-like appearance on imaging tests. Liver metastases from ovarian, pancreatic, colon, renal, or neuroendocrine cancer may have cyst‐like appearance on imaging tests.

features on CT and operative specimen. (A) CT, axial view. (B) CT, coronal view. (C) CT with i.v. contrast, axial view, after left lateral sectionectomy. (D) CT without contrast, axial view after left lateral sectionectomy. (E) Resected specimen after left lateral sectionectomy with hemorrhagic cystic feature on section. (F) Intraoperative aspect of the hepatic vascular tumor. (G) Resected specimen after atypical hepatectomies for the tumors located in the right lobe, with hemorrhagic cystic feature on section. **Figure 9.** Hepatomegaly caused by multiple bilateral liver vascular tumors with cystic features on CT and operative specimen. (A) CT, axial view. (B) CT, coronal view. (C) CT with i.v. contrast, axial view, after left lateral sectionectomy. (D) CT without contrast, axial view after left lateral sectionectomy. (E) Resected specimen after left lateral sectionecto‐ my with hemorrhagic cystic feature on section. (F) Intraoperative aspect of the hepatic vascular tumor. (G) Resected specimen after atypical hepatectomies for the tumors located in the right lobe, with hemorrhagic cystic feature on sec‐ tion.

**Figure 9.** Hepatomegaly caused by multiple bilateral liver vascular tumors with cystic

6
