CYSTIC NEOPLASMS OF THE PANCREAS

Abstract

Although all cystic neoplasms of the pancreas have relatively similar characteristics on modern imaging modalities, the cells of origin and their biologic aggressiveness are quite different and mandate a selective management approach. This spectrum of cystic disorders encompasses biologically diverse and questionably related diseases, which include the following four broad categories:

• 1
  Serous cystadenomas are composed of grapelike collections of predominantly small (< 2 cm), thin-walled, translucent cysts lined by a single layer of uniformly benign-appearing, glycogen-rich, serous cells.¹³ This category used to be referred to as microcystic neoplasm; however, this term is inappropriate and should be deleted from the current nomenclature.
• 2
  Mucinous cystic neoplasms (formerly known inappropriately as macrocystic neoplasms) represent a continuum ranging from (a) clinically and pathologically benign mucinous cystadenomas; (b) histologically dysplastic, aggressive-appearing, yet non-invasive proliferative mucinous cystic neoplasms that, if fully resected, do not recur;14, 20and, (c) rare malignant (tissue invasion) mucinous cystadenocarcinomas, which approach the biologic aggressiveness of typical ductal cancer of the pancreas. These mucinous cystic neoplasms are composed of mucin-containing cells that may express varying degrees of atypia, dysplasia, carcinoma in situ, and tissue invasion within the same tumor.
• 3
  Intraductal papillary mucinous tumor (IPMT) represents a newly recognized entity that also has been referred to most commonly as mucinous ductal ectasia. IPMT represents a spectrum of neoplastic processes composed of mucinous cells lining the main pancreatic duct or secondary pancreatic ducts.¹⁰ Significant controversy exists over whether IPMT represents a novel neoplasm arising from a different epithelium or a variant of mucinous cystic neoplasm involving the main pancreatic duct(s). Nevertheless, all agree that IPMT is a premalignant disorder that is recognized with increasing frequency. No reports of this disease existed before 1980. Whether IPMT truly represents a new entity (induced by environmental factors or a new mutation) or was previously overlooked and miscategorized as a ductal adenocarcinoma of the pancreas with mucinous differentiation is unclear; however, many of the clinical and imaging characteristics are so unique that it is hard to believe that it was merely overlooked in the past.
• 4
  Unusual cystic neoplasms include the extremely rare cystic islet cell tumors (functional and nonfunctional), acinar cell cystadenocarcinomas, cystic choriocarcinomas, cystic teratomas, and cystic lymphangiomatous neoplasms.²¹ These are all so unusual that they are not mentioned further in this article.