Gallbladder Adenocarcinoma with Florid Neuroendocrine Cell Nests and Extensive Paneth Cell Metaplasia

We report a unique case of gallbladder adenocarcinoma associated with florid neuroendocrine cell nests and extensive Paneth cell metaplasia that has not been described previously. The patient was a 79-yr-old woman with a pedunculated, polypoid mass in the gallbladder. Microscopically, the mass was composed at tumor cells showing tubular and papillary growth patterns, consistent with well-differentiated adenocarcinoma. One-third or more of the tumor cell showed Paneth cell appearance. Goblet cell-type tumors were also intermingled. In addition, neuroendocrine cell nests, that were connected to the neoplastic glands, were scattered throughout the stroma. lmmunohistochemically, the labeling index of MIB-1 in adenocarcinoma cells including Paneth cell-type carcinoma cells was approx 40%. Neuron-specific enolase, chromogranin A, and synaptophysin were positive in the neuroendocrine cells forming solid nests and intermingled within neoplastic glands. They were immunopositive for serotonin but negative for insulin, glucagon, somatostatin, and pancreatic polypeptide (PP). Although MIB-1-positive neuroendocrine cell nests were very few with weak staining, we think that the neuroendocrine cell nests were neoplastic in nature. The formation of the multifocal neuroendocrine nests may be a consequence of the trophic effects of unknown substance(s), which can promote serotonin producing neuroendocrine cells to proliferate. We postulate that Paneth cell-type carcinoma cells may be intimately related to such substance(s) in our case.