Undifferentiated spindle-cell carcinoma of the gallbladder: an immunohistochemical study.

A case of undifferentiated spindle-cell carcinoma of the gallbladder is described. A 72-year-old man presented with right hypochondralgia and fever. Imaging studies revealed a well-demarcated solid tumor (with a necrotic center) in the gallbladder that invaded the liver and transverse colon. On gross examination of the surgical specimen, the cut surface of the polypoid tumor showed nodular invasive growth. Microscopically, the tumor was composed of atypical spindle-shaped tumor cells that proliferated in a whirling or interlacing pattern. The tumor also showed foci with a malignant epithelial component that simulated a carcinosarcoma. Immunohistochemically, the biphasic differentiation of the tumor was highlighted by the different immunoreactivity to antibodies against cytokeratins, epithelial membrane antigen (EMA), and vimentin shown by the malignant epithelial components and the spindle-cell components. However the latter showed faint positivity for cytokeratin antibody. These results suggested that the spindle-cell carcinoma of the gallbladder originated from cholecystic mucosa and showed sarcomatous reaction or dedifferentiation, as indicated by the presence of vimentin-positive cells. The proliferation index, as detected by ki-67, in the spindle-cell component was higher than that in the epithelial component, which may account for the more aggressive biological behavior of the spindle-cell component.