A comparative study of seborrheic keratoses and basal cell epitheliomas by complement immunofluorescence and electron microscopy.

Eight cases of seborrheic keratosis (SK) and 7 cases of basal cell epithelioma (BCE) were studied comparatively by complement immunofluorescence using pemphigoid serum which was reactive not only to the basement membrane zone (BMZ) but also to the cell membrane or the intercellular space (CMICS) of basal cells in normal human epidermis. Positive immunofluorescence both at the BMZ and the CMICS of proliferating basaloid cells was observed in all cases of SK, whereas in BCE, immunofluorescence weaker than that in SK was observed only a the BMZ of tumor cell nests. These tumors were also examined by light and electron microscopy, and differences already described in the literature between SK and BCE were confirmed. These findings suggest that antigenic properties of the BMZ of the skin are affected by proliferating epithelial cells and that epithelial cells are involved in the formation of the BMZ.