Rare Malignant and Semimalignant Epithelial Neoplasms of the Biliary Tract

Abstract

The hepatobiliary tract is the site of an intriguing group of malignancies occurring in several other organs, extrapulmonary small cell carcinoma. In contrast to its bronchopulmonary counterpart, extrapulmonary small cell carcinomas occur with similar rates in female and male patients. With the exception of the gallbladder, the biliary tract is very rarely involved. Small cell carcinomas of the hepatobiliary tract belong to several categories, i.e., neuroendocrine type, mixed type, non-neuroendocrine type, and not otherwise specified types. Small cell carcinomas are highly aggressive neoplasms. Diagnosis and classification require immunohistochemical and molecular methods. Poorly differentiated or undifferentiated carcinomas of the bile ducts also include spindle cell carcinoma and carcinomas with rhabdoid features. Unusual neoplasms primary to the bile ducts also comprise hepatoid carcinoma and solid pseudopapillary tumor, a neoplasm better known from the pancreas.