Mucinous cystic neoplasms of the pancreas: update on the surgical pathology and molecular genetics.

Mucinous cystic neoplasms (MCNs) of the pancreas are primary pancreatic cyst-forming neoplasms that can be a precursor to invasive adenocarcinoma of the pancreas. MCNs occur almost exclusively in the distal pancreas of middle-aged women. MCNs typically show a "cyst-in-cyst" pattern of growth and are well encapsulated by a thick fibrous wall. MCNs are composed of mucin-producing neoplastic epithelial cells and "ovarian-type" subepithelial stroma. The epithelium is dysplastic and the grade can range from low to high grade; some MCNs have an associated invasive carcinoma. It is this associated invasive carcinoma that determines prognosis. MCNs harbor several characteristic genetic and epigenetic alterations, some of which are shared with conventional invasive pancreatic ductal adenocarcinoma. Furthermore, several studies reveal characteristic patterns of gene expression in the ovarian-type stroma that suggest steroidogenesis in the ovarian-type stroma. Better knowledge of the molecular alterations could help in the management of patients with this type of precursor of invasive carcinoma.