A case of primary neuroendocrine carcinoma of the gallbladder associated with anomalous union of the pancreaticobiliary duct.

Primary neuroendocrine carcinoma of the gallbladder is extremely rare because normal gallbladder mucosa does not contain neuroendocrine cells. Neuroendocrine cells can be detected at sites of intestinal metaplasia induced by chronic inflammation, which may be the initial step in the development of neuroendocrine tumor of the gallbladder. Anomalous union of the pancreaticobiliary duct (AUPBD) is an uncommon congenital anomaly that is frequently associated with choledocholithiasis, cholangitis, pancreatitis, and cancer of the gallbladder or bile duct. In AUPBD, cancers of the gallbladder and bile duct can be induced by chronic inflammation. We report herein a case of large-cell neuroendocrine tumor of the gallbladder associated with AUPBD.