Mucinous Cystic Neoplasms

Abstract

Mucinous cystic neoplasm (MCN) of the pancreas is one of the three most common primary cyst-forming epithelial neoplasms of the pancreas including intraductal papillary mucinous neoplasm (IPMN), serous cystic neoplasm (SCN) and MCN. From another point of view, MCN is one of the three precursors of invasive adenocarcinoma of the pancreas including pancreatic intraepithelial neoplasia (PanIN), IPMN and MCN. MCNs occur almost exclusively in the distal pancreas of middle-aged women. Grossly, MCNs typically show a “cyst-in-cyst” pattern of growth, and are well encapsulated by a thick fibrous wall. In histology, MCNs are composed of mucinous neoplastic epithelial cells and subepithelial cellular stroma called as “ovarian-type” stroma. The epithelium is dysplastic and the grade can be divided into low- and high-grade, and some MCNs have an associated invasive carcinoma. MCNs harbor several characteristic genetic and epigenetic alterations, some of which are shared with conventional invasive pancreatic ductal adenocarcinoma. Several studies suggest steroidogenesis in the “ovarian-type” stroma. A 5-year survival rate of non-invasive MCN is 100%, and MCN with T1a and T1b carcinoma also had an excellent prognosis. However, in one study, MCN with invasive carcinoma show aggressive clinical course; a 3-year and 5-year survival rate are 44% and 26%, respectively. In European guidelines, MCNs <40 mm are treated conservatively when other risk factors are absent. In international and American guidelines, on the other hand, an MCN of any size is an absolute indication for resection. Better knowledge of the pathology and molecular alterations could help in the management of patients with MCN.