Small cell (endocrine cell) carcinoma of the gallbladder in a 62‐year‐old woman is reported. The palliative cholecystectomy specimen revealed a submucosally invading tumor with extensive hemorrhagic necrosis. At autopsy, performed five months after surgery, a huge tumor measuring 14×12×8cm was located at the liver hilus. No signs or symptoms related to overproduction of hormones were recorded throughout her illness. Neither lung lesions nor gall stones were identified. Histologically, diffuse proliferation of small, spindle shaped atypical tumor cells with numerous mitoses was evident. Intraepithelial tumor cell proliferation in the gallbladder mucosa was seen focally. The neuroendocrine nature of the tumor cells was confirmed by the histologic pattern of growth with pseudo‐rosette formation, positive reaction for Grimelius' argyro‐philia, neuron‐specific enolase and Leu 7, and ultra‐structural demonstration of neuroendocrine‐type granules. Immunostaining for a variety of hormones was all negative. Characteristically, foci with squamous and adenocarcinomatous differentiation were identified in the tumor tissue. The glandular components were immuno‐reactive for carcinoembryonic antigen, secretory component, epithelial membrane antigen and CA19–9. The histogenesis and totipotentiality of the neop
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