Oat cell carcinoma of the gallbladder. A rare and highly lethal neoplasm.

Oat cell carcinomas arising in the gallbladder are an extremely rare and aggressive form of gallbladder cancer. These neoplasms are morphologically identical to their pulmonary counterparts, contain neurosecretory granules on ultramicroscopic examination, and demonstrate immunohistochemical staining for cytokeratin, neuron-specific enolase, and other neuroendocrine markers. Oat cell carcinomas typically occur in elderly women with cholelithiasis, and pursue a fulminant course with extensive metastases, especially to the liver. The mean survival is less than 7 months. We present a well-documented case of oat cell carcinoma of the gallbladder and review the literature on this unusual entity.