Mucin hypersecreting neoplasms.

Mucinous pancreatic neoplasms are uncommon disorders classified as either mucinous cystic neoplasms (mucinous cystadenoma or cystadenocarcinoma) or the more recently described intraductal mucin hypersecreting neoplasms (IMHN), also termed mucinous ductal ectasia. The mucinous cystic neoplasms share many common features with IMHN's but remain distinct clinico-pathologic entities. These tumors have similar histologic appearances, produce abundant mucin, are likely to masquerade as pancreatic pseudocysts, demonstrate a biologically less aggressive course compared to typical ductal adenocarcinomas, and are treated by surgical resection. Nevertheless, IMHN is characterized by intraductal tumor growth and mucin hypersecretion causing cystic transformation of the pancreatic duct and producing a distinct appearance on ERCP of mucus extrusion through a widely patent papilla and amorphous filling defects within the duct. In contrast, the mucinous cystic tumors are proposed to secrete mucin into a peripheral branch duct leading to a cyst cavity which does not communicate with the pancreatic duct and therefore is not demonstrated on pancreatography.