Ber-EP4-positive phenotype differentiates actinic keratosis from superficial basal cell carcinoma

BACKGROUND. Well-defined histopathologic criteria exist to distinguish acti nic keratosis (AK) from superficial basal cell carcinoma (BCC). A similar m orphology of downwardly budding dysplastic keratinocytes may occur in both entities, creating potential for errors in diagnosis. A marker that could r eliably distinguish these two lesions would overcome this difficulty in dia gnosis. OBJECTIVE. TO investigate whether Ber-EP4 staining is useful in distinguish ing AK from superficial BCC, and to determine whether AK exhibits a cellula r phenotype that is more consistent with BCC or squamous cell carcinoma (SC C). METHODS. We subjected tissue sections from superficial BCC, AK, and squamou s intraepithelial neoplasia (SIN) demonstrating epidermal budding to immuno histochemical staining with monoclonal antibody Ber-EP4. RESULTS. Abnormal keratinocytes in all specimens of superficial BCC (5 of 5) were Ber-EP4 pos itive; all AK (10 of 10) and SIN (8 of 8) were Ber-EP4 negative. CONCLUSION. Ber-EP4 staining reliably distinguishes AK from superficial BCC . The lack of Ber-EP4 staining of AK supports the currently accepted pathog enetic dogma that SIN and SCC arise from AK, but BCC does not.