Undifferentiated carcinoma of the gallbladder with endothelial differentiation: A case report and literature review.

Undifferentiated carcinoma of the gallbladder is a rare cancer type with a poor prognosis. The present study described a case of undifferentiated gallbladder carcinoma of the spindle- and giant-cell type, according to the 2010 World Health Organization classification. Hematoxylin and eosin staining revealed that the tumor consisted of dense interlacing bundles of spindle-shaped cells. No evidence of cartilaginous, osseous or rhabdomyosarcomatous differentiation was observed. Immunohistochemical staining revealed that spindle- and polygonal-shaped cells of the undifferentiated carcinoma were positive for cytokeratin AE1/3, vimentin and vascular endothelial growth factor. Furthermore, numerous spindle-shaped cells were positive for cluster of differentiation (CD)34 and CD31, and certain spindle-shaped cells were positive for Factor VIII. These results suggested classification of the present case as 'undifferentiated gallbladder carcinoma with endothelial differentiation'.