Composite endocrine cell, typical adenocarcinoma and signet ring carcinoma of the gallbladder.

The authors report a case of composite tumor of the gallbladder which exhibited features of both adenocarcinoma (with typical areas, signet ring cells and clear cells) and endocrine cell carcinoma. The histological picture suggests the origin of both components in a common primitive cell with the capacity to differentiate to different types of metaplastic epithelium and supports the hypothesis of a sequence metaplasia--dysplasia--carcinoma.