Neuroendocrine carcinoma of the extrahepatic biliary tract with positive immunostaining for gastrin-releasing peptide: report of a case.

We report herein the first documented case of gastrin-releasing peptide-positive neuroendocrine (NE) carcinoma of the extrahepatic biliary tract. An invasive tumor measuring 2.5 x 1.5 cm was located in the confluence portion of the cystic duct in a 70-year-old Japanese man. Histologically, the tumor was found to be composed of small polygonal cells which formed a solid and trabecular structure, and the frequencies of both mitoses and small necrotic areas were dominant. The tumor cells were immunoreactive to the NE markers chromogranin-A and neuron-specific enolase, as well as to carcinoembryonic antigen and gastrin-releasing peptide. Although a few cases of gastrin-releasing peptide-positive small-cell lung carcinoma have been documented, there have been no reports of gastrin-releasing peptide-positive NE carcinoma occurring in the gastrointestinal tract. We consider our case not merely to be of pathological interest, but also to have clinical and therapeutic implications.