**4. Serous cystic neoplasms (SCNs)**

**No lining →** Pseudocysts (pancreatitis associated)

MCNs IPMNs

SCNs

VHL‐associated pancreatic cysts

Acinar cell cystadenocarcinomas

In the autopsy series, the prevalence reaches 24% [8]. All cystic tumors of the pancreas reach about 10–15% of all cystic pancreatic lesions [7]. The exact prevalence of cystic pancreatic tumors is not defined. Autopsy study shows a prevalence of 24.3%; however, imaging studies have found the prevalence of 1.2–2.4%. On the other hand, pseudocystic lesions reach 90% of all pancreatic cystic lesions but only 45% of these patients had previous pancreatitis [6]. The economic impact that is necessary to follow these patients by imaging studies should be

The epidemiologic and demographic features are different in the several types of cystic tumors,

The current use of imaging modalities has allowed some important results in the nosographic study: certain distinction between postnecrotic acute or chronic pseudocysts and cystic tumors; among the cystic neoplasms, the identification of clinical pathological features that allow recognizing some kinds of cystic tumors with several perspective of neoplastic evolution.

Lymphoepithelial cysts

Lymphangiomas

**Table 2.** Classification of cystic lesions of the pancreas [5].

and they will be presented in specific sections.

**3. Diagnostic perspectives and management options**

**Degenerative necrotic changes in a neoplasm**

**Lining**

Mucinous epithelium

96 Challenges in Pancreatic Pathology

Serous epithelium

Squamous epithelium

Endothelial lined cysts

Cystic ductal adenocarcinomas

Acinar cells

SPPNs CPENs

evaluated.

SCNs can be divided into serous cystadenoma and serous cystadenocarcinoma. Serous cystadenoma is a benign neoplasm consisting of uniform glycogen‐rich epithelial cells that give rise innumerable small cysts containing serous fluid. These lesions arise from centroacinar cell‐intercalated duct system [11, 12], producing MUC6.

Histological and immunohistochemical data characterize the morphology and pathological evolution of serous cystadenoma. The cells lining the small cysts have clear cytoplasm with well‐defined border and round uniform nuclei. They are negative for mucin stains; in these, lesions are not present the molecular genetic alterations, specific of mucinous‐type ductal pancreatic neoplasia such as mutation in the K‐ras, SMADH4/DPC4, TP53, and p16 genes [13]. In the pathogenesis of serous cystadenomas, the alterations of von Hippel‐Lindau (VHL) gene have been demonstrated in 40% of cases [3]; therefore, serous cystadenomas are associated with von Hippel‐Lindau syndrome, an autosomal dominant disorder, characterized by hemangioblastoma of central nervous system and retina, renal cysts and neoplasms, and phaeochromocytomas. The pancreatic cystic lesions in VHL syndrome usually develop earlier than central nervous system lesions.

The relative frequency of serous lesions into cystic pancreatic neoplasms ranges from 20 to 30%.

The SCNs occur predominantly in female patients (female/male ratio 3:1) of sixth–seventh decade. Almost 70% of SCNs occur in the body or tail of the pancreas and 30–40% of the patients are asymptomatic, and the lesions are detected incidentally. Symptomatic patients can present some trouble caused by size of the neoplasm such as abdominal pain, discomfort, malaise, anorexia, or objective signs as palpable mass, jaundice, and weight loss.

On imaging studies (CT or MRI), SCNs may present with two main morphologies: the more frequent, classic microcystic appearance and the less common oligocystic appearance.

Microcystic‐type lesions present multiple small cysts, in one‐third of cases with a central fibrous scar and calcification creating a sponge‐like appearance, which can be considered pathognomonic. The size of the mass, much variable, ranges from few centimeters to 20–25 cm.

There are rare cases of oligocystic‐type pattern (megacystic and macrocystic). This type consists of fewer and larger loculi, with lobulated contour without wall enhancement and usually is located in the pancreatic head [14]. The epithelial lining of these cysts may become denuded and can be difficult to distinguish from mucinous neoplasms. In this case, it can be useful to identify the characteristic glycogen‐rich clear cells [15].

On EUS, the SCNs show multiple, small, anechoic cysts and thin septations. There is a vascular network on cyst wall. The aspirated cyst‐fluid from EUS‐FNA is low in CEA concentration, and the result of cytology is poor.

For SCNs, the risk of malignancy is <1%. SCNs with certain clinical diagnosis, little in size, from 2–2.5 to 4–5 cm, asymptomatic can be observed. The criteria of the control are based on increase of the size lesion and increase of the tumor markers (CEA). Beside the benign serous cystadenomas that are the majority of cases, there are also few malignant lesions, serous cystadenocarcinomas [16]. The structural histological findings are overlappable between serous cystadenoma and cystadenocarcinoma, and often only the metastatic potential should distinguish the malignant variants.

In the SCNs, the certainty of the preoperative diagnosis is most important for the therapeutic choice between non‐operative management with follow‐up and surgical treatment. Three criteria should be evaluated for surgery: likelihood of malignant evolution, symptoms caused by increase of the size of the tumor, and age of the patient.

Malignant SCNs constitute <3% of all SCNs [17], but within these cases, there are also serous cystadenocarcinomas not as evolution of benign tumors. Therefore, the global risk of malig‐ nancy of SCNs is <1% [18, 19].

A lot of the patients are asymptomatic at the diagnosis (incidental diagnosis). The likelihood of symptoms increases with the size of tumor. In fact, 22% of the patients is symptomatic with tumor <4 cm in diameter, but for tumor more than 4 cm, 77% of the patients becomes symp‐ tomatic [19].

The average age at the diagnosis frequently is 65 years or more.

well‐defined border and round uniform nuclei. They are negative for mucin stains; in these, lesions are not present the molecular genetic alterations, specific of mucinous‐type ductal pancreatic neoplasia such as mutation in the K‐ras, SMADH4/DPC4, TP53, and p16 genes [13]. In the pathogenesis of serous cystadenomas, the alterations of von Hippel‐Lindau (VHL) gene have been demonstrated in 40% of cases [3]; therefore, serous cystadenomas are associated with von Hippel‐Lindau syndrome, an autosomal dominant disorder, characterized by hemangioblastoma of central nervous system and retina, renal cysts and neoplasms, and phaeochromocytomas. The pancreatic cystic lesions in VHL syndrome usually develop earlier

The relative frequency of serous lesions into cystic pancreatic neoplasms ranges from 20 to

The SCNs occur predominantly in female patients (female/male ratio 3:1) of sixth–seventh decade. Almost 70% of SCNs occur in the body or tail of the pancreas and 30–40% of the patients are asymptomatic, and the lesions are detected incidentally. Symptomatic patients can present some trouble caused by size of the neoplasm such as abdominal pain, discomfort, malaise,

On imaging studies (CT or MRI), SCNs may present with two main morphologies: the more frequent, classic microcystic appearance and the less common oligocystic appearance.

Microcystic‐type lesions present multiple small cysts, in one‐third of cases with a central fibrous scar and calcification creating a sponge‐like appearance, which can be considered pathognomonic. The size of the mass, much variable, ranges from few centimeters to 20–25

There are rare cases of oligocystic‐type pattern (megacystic and macrocystic). This type consists of fewer and larger loculi, with lobulated contour without wall enhancement and usually is located in the pancreatic head [14]. The epithelial lining of these cysts may become denuded and can be difficult to distinguish from mucinous neoplasms. In this case, it can be useful to

On EUS, the SCNs show multiple, small, anechoic cysts and thin septations. There is a vascular network on cyst wall. The aspirated cyst‐fluid from EUS‐FNA is low in CEA concentration,

For SCNs, the risk of malignancy is <1%. SCNs with certain clinical diagnosis, little in size, from 2–2.5 to 4–5 cm, asymptomatic can be observed. The criteria of the control are based on increase of the size lesion and increase of the tumor markers (CEA). Beside the benign serous cystadenomas that are the majority of cases, there are also few malignant lesions, serous cystadenocarcinomas [16]. The structural histological findings are overlappable between serous cystadenoma and cystadenocarcinoma, and often only the metastatic potential should

In the SCNs, the certainty of the preoperative diagnosis is most important for the therapeutic choice between non‐operative management with follow‐up and surgical treatment. Three

anorexia, or objective signs as palpable mass, jaundice, and weight loss.

identify the characteristic glycogen‐rich clear cells [15].

and the result of cytology is poor.

distinguish the malignant variants.

than central nervous system lesions.

98 Challenges in Pancreatic Pathology

30%.

cm.

The choice of treatment of SCNs can be summarized. We can consider several cases:


In summary, surgical indications for SCNs with certain diagnosis (imaging, fluid cyst evalua‐ tion, etc.) are based on serious symptoms, great size tumors, or great increase of the size tumor in patient diagnosed and followed over time and increase of tumor marker (CEA) in fluid cyst [20].
