Primary Mixed Adenoneuroendocrine Carcinoma of the Gallbladder in a 55-Year-Old Female Patient: A Case Report and Review of the Literature.

Mixed adenoneuroendocrine carcinomas (MANECs) of the biliary tract are rare tumors, and to date only a few cases arising in the gallbladder have been reported. Their histogenesis is a matter of debate, since the biliary tract normally lacks neuroendocrine cells. However, the immunohistochemical identification of nonneoplastic neuroendocrine cells in both biliary adenocarcinomas and intestinal metaplasia has been documented. Here we report a case of a 55-year-old female patient presenting with right upper quadrant pain, cholelithiasis, and a gallbladder mass identified after cholecystectomy. The histopathologic examination showed a MANEC, composed of an intestinal-type adenocarcinoma and a large cell neuroendocrine carcinoma, arising in a background of enteric metaplasia with extensive high-grade dysplasia. Moreover, we report the presence of focal pancreatic intraepithelial neoplasia-like epithelial lesions, which has not been described for these tumors yet. The histopathologic features of this case provide further support for the theory that MANECs arise following a metaplasia-dysplasia-carcinoma pathway.