Caveats in BerEP4 staining to differentiate basal and squamous cell carcinoma

Background Superficial skin biopsies of basal cell carcinoma (BCC) represent some of the most common dermatopathology specimens. Superficial shave biopsies containing partial samples of lesions with squamatization present difficulties in distinguishing BCC from squamous cell carcinoma (SCC). BerEP4 has been employed as a dependable marker in differentiating between BCCs and SCCs. Methods We collected 12 cases of superficial biopsies of BCC with centrally located cords and strands suggesting squamous differentiation at the Yale Dermatopathology Laboratory over a 3-month period and stained them with BerEP4. Results We found that all cases (12 out of 12) showed membranous and cytoplasmic staining with BerEP4 in the obvious areas of basaloid differentiation at the periphery of the tumors, while cords and strands of enlarged cells with squamoid features in the center and surface of the biopsy failed to label with BerEP4. Conclusions BerEP4 labeling is not reliable in superficial biopsies of BCC with squamoid features. It is important to be aware of this caveat in interpreting BerEP4 staining for BCC and SCC. Yu L, Galan A, McNiff JM. Caveats in BerEP4 staining to differentiate basal and squamous cell carcinoma.