Composite glandular–endocrine cell carcinoma of the common bile duct

A rare case of composite glandular–endocrine cell carcinoma of the common bile duct is presented. Histologically, this tumor consisted of adenocarcinoma and small‐cell neuroendocrine carcinoma, with a transition between the two components. The two distinct areas of the tumor were immunohistochemically different, whereas the transitional zone exhibited characteristics of both areas. These features suggest that the tumor arose from a multipotential stem cell. Although it has been reported that the presence of neuroendocrine differentiation in carcinomas indicates a poor prognosis, the patient in the present case was well at the time of writing this report. This may be due to the fact that adenocarcinoma, which characteristically has a low proliferative activity, constituted the majority of the tumor.