A case of lipid-rich neuroendocrine tumor of the gallbladder mimicking a cholesterol polyp

Abstract Neuroendocrine tumors (NETs) are rare in the gallbladder possibly because of paucity of the precursor neuroendocrine cells in this organ. Lipid-rich NET (LR-NET), also known as clear cell NET, is a rare but distinct variant of NET observed in various organs. In the gallbladder of the case reported herein, there was a pedunculated polypoid mass of golden-yellow in color which macroscopically mimicked a cholesterol polyp, albeit somewhat larger. Histologically the polyp showed accumulation of foamy lipid containing cells in the lamina propria covered by normal columnar epithelial cells, thus again resembling a cholesterol polyp. However, the foamy cells often showed ribbon-like arrangement and were immunohistochemically strongly positive for neuroendocrine markers. This report represents gross and microscopic features, including fat stain, of a peculiar type of LR-NET in the gallbladder. A rare but important differential diagnostic consideration in cholesterol polyp-like lesions seen on cholecystectomy specimens is presented.