KERATOACANTHOMA - A DEFICIENT SQUAMOUS-CELL CARCINOMA - STUDY OF BCL-2 EXPRESSION

Ten keratoacanthomas with both proliferative and regressive histologic features along with 10 well-differentiated squamous cell carcinomas w ere examined using immunohistochemistry for the expression of bcl-2, a protooncogene recently recognized to be involved in protecting cells from undergoing apoptosis. The squamous cell carcinomas had a modest b ut diffuse staining pattern, while the proliferative keratoacanthomas stained only at the basal cells and only rare cells stained positively in the regressive keratoacanthomas. The degree and pattern of stainin g suggest a loss of bcl-2 expression with tumor maturity in keratoacan thoma and a possible role in their ultimate involution.