Neuroendocrine Carcinoma and Intracystic Papillary Neoplasm: A Rare Association in the Gallbladder.

Neuroendocrine carcinoma of the gallbladder is a very rare neoplasia comprising only 0.2% of all the gastrointestinal neuroendocrine tumors. We present the case of an 85-year-old male with nonspecific gastrointestinal symptoms, progressive weight loss, and deterioration in the preceding 15 days. Imaging study showed a 5-cm polypoid mass localized at the gallbladder fundus, leading to a radical cholecystectomy. Pathology revealed the known lobulated polypoid lesion, on cut section, constituted by friable tissue without evident infiltration of the gallbladder wall and a contiguous friable, brown, flat lesion. Histological evaluation displayed a small cell neuroendocrine carcinoma, consisting of intermediate and small cells, rounded or spindle, with extensive areas of necrosis, with positivity for neuroendocrine immunomarkers, associated with intracystic papillary neoplasm with high and low dysplasia. This is an uncommon association with few cases presented in the literature.