Chapter 148: Mucinous Cystic Neoplasms of the Pancreas

OVERVIEW

Cystic neoplasms of the pancreas represent a diagnostic challenge for physicians. Once considered rare, over the past two decades the identification of these cysts has increased secondary to the improvement and widespread use of cross-sectional imaging studies.¹ A considerable proportion of these lesions are discovered incidentally in asymptomatic patients and are found with greater frequency in older populations.^2,3

The significance of pancreatic cystic neoplasms (PCNs) lies in the spectrum of their underlying pathology. Since they were first distinguished from serous neoplasms in the late 1970s, mucinous pancreatic cystic neoplasms (MPCNs) have been extensively studied.⁴ Unlike serous cystic neoplasms (SCNs), MPCNs harbor the potential for malignant degeneration. Although the risk is higher in symptomatic patients, up to 47% of MPCNs are associated with malignant or premalignant lesions, making early detection and treatment essential.^5,6

Mucinous pancreatic cystic neoplasms account for up to one-fourth of all PCNs and include two distinct classes of cysts. Besides their common underlying cancer risk and viscous quality, these MPCN variants possess distinct clinicopathologic features that dictate their presentation and behavior. Furthermore, the risk of malignant degeneration varies widely between subtypes.⁷ Within the broad category of MPCNs exists a spectrum of atypia, ranging from benign adenoma to grossly invasive cancer.

Mucinous cystic neoplasms (MCNs) are known to contain ovarian-type stroma and are almost exclusively found in women within the distal pancreas.^8,9 In contrast, intraductal papillary mucinous neoplasms (IPMNs) are mainly localized to the head of the pancreas and are characterized by intraductal proliferation of neoplastic cells whose phenotype and behavior are characterized by the type of ductal communication.⁸ Of the three IPMN variants, branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs) account for the majority of all pancreatic cysts found incidentally and pose the biggest challenge for diagnosis and cancer risk stratification.¹⁰

The workup and diagnosis are critical in deciding the ultimate management of MPCNs. Although each cyst type is associated with a particular radiographic profile, imaging studies alone are often insufficient to render a diagnosis. Use of endoscopic ultrasound (EUS) with cyst fluid analysis has become an important tool to differentiate between cyst types and may be used in the diagnosis and surveillance of pancreatic cysts.¹¹

Accurate diagnosis of pancreatic cyst types may ultimately prevent unnecessary resection by selecting those premalignant lesions that require intervention and those that may be closely observed. Over the last decade, international consensus guidelines have been developed with the intent to provide direction when managing patients with MPCNs.^12,13 Correct identification and stratification of these entities is paramount to MPCN management and treatment.

INCIDENCE AND EPIDEMIOLOGY

The rising incidence of pancreatic cysts has been extensively reported in the literature. In one study, incidental pancreatic cysts were found in up to 13.5% of patients on routine ...