Epithelioid cell histiocytoma: a new entity.

This is a report of a previously undescribed type of histiocytoma distinguished clinically by its occurrence as a solitary elevated nodule often with a vascular appearance and cytologically by the presence of large angulated epithelioid cells. Nineteen lesions from 11 women and eight men have been studied. The lower limb was the commonest site for the nodules. The mean age at presentation was 42 years (range 23-63). Only one lesion recurred after attempted removal. This lesion in the past may, have been mistaken for a Spitz naevus. Immunohistochemical findings mirror those of ordinary histiocytomas. In particular approximately 50% of the constituent cells label with a polyclonal antibody directed against factor XIIIa--an antibody that labels dermal fixed connective tissue cells (fibrocytes) and cells in ordinary histiocytoma, but not the cells of Spitz or common melanocytic naevi.