**2. Classifications and epidemiology**

The recent WHO classification 2010 of all pancreatic tumors is more extensively used. This classification encompasses epithelial tumors (benign, premalignant lesions, malignant lesions, and neuroendocrine neoplasms), mesenchymal tumors, lymphomas, and secondary tumors [1].

Based on pathological, clinical and radiologic assessments, some not recent but valuable [2], several classifications of cystic pancreatic neoplasms and lesions have been proposed. We believe interesting to note the proposed classification that fully includes all cystic lesions of the pancreas [3]. This classification includes the following cystic lesions: neoplastic epithelial (benign, borderline, and malignant), non‐neoplastic epithelial, neoplastic non‐epithelial (very rare), and non‐epithelial non‐neoplastic (very rare).

The frequency of each cystic lesions is not defined with precision, may be for observers diversity (surgeons, radiologists, and pathologists) and for the assessment of different developmental stages of lesions.

Pancreatic cystic tumors comprise a variety of neoplasms with a wide range of malignant potential: benign, borderline, and malignant. The classification proposed by Kosmahl encom‐ passes the majority of the recently now described lesions (**Table 1**).

Many cystic neoplasms listed in the classifications are infrequent or rare pathological varieties, with minimal and not evident clinical characterization [4]. The simplified classification can be proposed that comprises two groups of lesions:



**Table 1.** Classification of cystic neoplasms and lesions of pancreas [3].

**1. Introduction**

94 Challenges in Pancreatic Pathology

of the diagnosis.

**2. Classifications and epidemiology**

rare), and non‐epithelial non‐neoplastic (very rare).

proposed that comprises two groups of lesions:

passes the majority of the recently now described lesions (**Table 1**).

developmental stages of lesions.

role.

[1].

Cystic lesions of the pancreas are less frequent in relation to solid neoplasies. These lesions have attracted new and great interest. In the last several decades, the knowledge of the cystic neoplasms has enlarged and the management has changed dramatically. The wide adoption in the diagnostic procedures of routine and advanced imaging such as ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance chol‐ angiopancreatography (MRCP), and endoscopic ultrasound (EUS) has become the cornerstone

EUS‐guided fine needle aspiration (FNA) can allow the assessment of tumor markers, chemistries, cytology, and DNA analysis. Also pathological study has played a very important

The recent WHO classification 2010 of all pancreatic tumors is more extensively used. This classification encompasses epithelial tumors (benign, premalignant lesions, malignant lesions, and neuroendocrine neoplasms), mesenchymal tumors, lymphomas, and secondary tumors

Based on pathological, clinical and radiologic assessments, some not recent but valuable [2], several classifications of cystic pancreatic neoplasms and lesions have been proposed. We believe interesting to note the proposed classification that fully includes all cystic lesions of the pancreas [3]. This classification includes the following cystic lesions: neoplastic epithelial (benign, borderline, and malignant), non‐neoplastic epithelial, neoplastic non‐epithelial (very

The frequency of each cystic lesions is not defined with precision, may be for observers diversity (surgeons, radiologists, and pathologists) and for the assessment of different

Pancreatic cystic tumors comprise a variety of neoplasms with a wide range of malignant potential: benign, borderline, and malignant. The classification proposed by Kosmahl encom‐

Many cystic neoplasms listed in the classifications are infrequent or rare pathological varieties, with minimal and not evident clinical characterization [4]. The simplified classification can be

**•** Non‐mucinous cystic lesions: inflammatory pseudocysts without a true epithelial lining (in the setting of acute and chronic pancreatitis), serous cystic neoplasms (SCNs), solid pseudopapillary neoplasms (SPPNs), and cystic pancreatic endocrine neoplasms (CPENs). **•** Mucinous cystic lesions (epithelial lining produces mucinous cyst fluid): intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs).

This classification highlights as criterion of differentiation the presence of mucinous epitheli‐ um characterized by malignant potential.

Another criterion of classification of cystic lesions of pancreas is based on the epithelium lining of the cyst (**Table 2**).

In summary, the most common neoplasms include: serous cystic neoplasms (SCNs)/serous cystadenoma, mucinous cystic neoplasms (MCNs), intraductal papillary mucinous neoplasms (IPMNs), solid pseudopapillary neoplasms (SPPNs), and cystic pancreatic endocrine neo‐ plasms (CPENs). There are others rare or very rare tumors: acinar cells cystadenoma, cysta‐ denocarcinoma, cystic teratoma (dermoid cyst), and cystic pancreatoblastoma. Pancreatic cystic tumors are rare and less frequent than others pancreatic tumors. Image‐based studies show prevalence of pancreatic cystic lesions ranging from 1.2 to 19% [6, 7].

```
No lining → Pseudocysts (pancreatitis associated)
Lining
Mucinous epithelium
                   MCNs
                   IPMNs
Serous epithelium
                   SCNs
                   VHL‐associated pancreatic cysts
Squamous epithelium
                   Lymphoepithelial cysts
Acinar cells
                   Acinar cell cystadenocarcinomas
Endothelial lined cysts
                   Lymphangiomas
Degenerative necrotic changes in a neoplasm
SPPNs
CPENs
Cystic ductal adenocarcinomas
```
**Table 2.** Classification of cystic lesions of the pancreas [5].

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 evaluated.

The epidemiologic and demographic features are different in the several types of cystic tumors, and they will be presented in specific sections.
