Spindle cell carcinoma is a rare malignant tumor which is generally considered to be a variant of squamous cell carcinoma. A case of spindle cell carcinoma of the tongue occurring in a 50-year-old Chinese male is reported. Immunohistochemical technique was used as an adjunct to the diagnosis of this unusual type of carcinoma. The immunohistochemical expression of keratin was recognized in the spindle cells, as well as in the carcinomatous cells. Moreover, the spindle cell component expressed vimentin. These findings suggest an epithelial origin with squamous differentiation and mesenchymal participation in the genesis of spindle cell carcinoma. Additionally, the differential expression of low and high molecular weight keratin was demonstrated. The possible causes of coexpression of keratin and vimentin are also briefly reviewed, which may be because some epithelial tumor cells were transformed into mesenchymal (vimentin-positive) spindle cells; or due to dedifferentiation, with regression to vimentin, an embryonal type of intermediate filament; or attributed to the cellular adaptation to environmental influences; or be related to reduced cell-to-cell contact.