Large cell neuroendocrine carcinoma of the gallbladder. Report of two cases.

We report two cases of primary large cell neuroendocrine carcinoma (LCNEC) of the gallbladder, which, to the best of our knowledge, represent the first description of this entity. One of the tumors consisted entirely of LCNEC, whereas the second tumor was composed of LCNEC and the more common intestinal-type adenocarcinoma. Both tumors were morphologically similar to their pulmonary counterpart and were characterized by large cells with prominent nucleoli, coarse chromatin, and a high mitotic rate. The cells showed an organoid growth pattern with rosette formation and frequent areas of necrosis. Panendocrine markers were expressed in a variable proportion of tumor cells in both cases, and one of the cases also showed focal positivity for type 2 somatostatin receptors. One of the tumors followed a rapidly fatal course despite aggressive surgical treatment and chemotherapy administration, and the second patient is still alive and disease-free 12 months after surgery. The description of these two cases of LCNEC of the gallbladder is significant for two reasons. From an academic standpoint, we now know that all the neuroendocrine tumors described in other organs can arise de novo in the gallbladder. More importantly, however, the recognition of this rare tumor type carries important clinical implications in regard to the use of chemotherapeutic agents and supplemental treatments (for example, somatostatin analogs).