A rare case of small cell carcinoma (SCC) of the gallbladder combined with adenocarcinoma is reported. The patient was a 70‐year‐old Japanese man, who died of the disease shortly after the onset of symptoms. Autopsy disclosed a small tumor (1.0 cm in longest diameter) in the fundus of the gallbladder, with widespread metastasis. Histochemically, the tumor cells showed negative reactions for argyrophilic and argentaffin stainings, a weak immunohistochemical reaction only for neuron‐specific enolase, and negative reactions for all of the other neurosecretory markers used, including neurofilament, chromogranin, somatostatin, gastrin and leu‐7. However, electron microscopic examination revealed a few typical neurosecretory granules (NSG) in the cytoplasm of some tumor cells. We suggest that: 1. The presence of NSG in the cytoplasm of tumor cells is the most reliable diagnostic criterion for SCC. 2. SCC, at least the combined type, arises from a multipotential st
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