Spindle cell squamous cell carcinoma not expressing stratified but simple epithelial cytokeratin: efficacy of simple epithelial cytokeratin immunoreactivity.

We present two cases of spindle cell squamous cell carcinoma, which were derived from solar keratosis and burn scar in two elderly Japanese patients, respectively. The tumors involved the whole dermis and subcutis in connection with the overlying epidermis. They were composed mainly of anaplastic spindle cells partially forming storiform patterns. The tumor cells were diffusely positive for vimentin and cytokeratin 8/18 (clone CAM5.2, simple epithelial cytokeratin), but negative for cytokeratin 1/5/10/14 (clone 34βE12, stratified epithelial cytokeratin). Ultrastructural analysis of a patient demonstrated desmosomes and tonofilaments in the tumor cells. Although spindle cell squamous cell carcinoma is usually positive for vimentin, detailed cytokeratin profile is controversial. The present cases revealed immunohistochemistry not expressing stratified but simple epithelial cytokeratin and vimentin. We should be reminded of the efficacy of simple epithelial cytokeratin immunoreactivity in spindle cell squamous cell carcinoma.