IPMN : Differential
Differential diagnosis of intraductal papillary mucinous neoplasms (IPMNs) of pancreas includes pancreatic intraductal neoplasms (PanIN), mucinous cystic neoplasm (MCN), and retention cysts. The distinction of IPMN from MCN is addressed in the slide.
PanIN is a microscopic (usually < 5mm), papillary or flat, noninvasive, epithelial neoplasm arising in the pancreatic ducts. It lined by columnar or cuboidal epithelium with varying amounts of mucin and degrees of cytologic and architectural atypia. A large PanIN may be difficult to separate from small gastric-type IPMN. If the lesion is lined by intestinal or pancreatobiliary epithelium, it favors IPMN.
Pancreatobiliary IPMN resemble intraductal tubulopapillary neoplasms (ITPN). Features favoring ITPN include tubulopapillary architecture, high-grade dysplasia, minimal to no intracellular mucin, and no expression of MUC5AC. Intraductal lesions that are 0.5 to 1.0 cm in size, have papillary architecture and are lined by intestinal epithelium can be labeled as incipient IPMN.
Retention cysts: They are unilocular dilatation of the pancreatic ducts secondary to an obstruction. They are lined by a single layer of flattened or cuboidal epithelium with no cytologic atypia.