A specific antigenic defect of the basement membrane is found in basal cell carcinoma but not in other epidermal tumors.

The basement membrane of basal cell carcinoma was characterized by indirect immunofluorescence using antibodies to laminin, type IV collagen, and bullous pemphigoid antigen, three distinct protein components of basement membrane. Aggregates of basal cell carcinoma in the dermis were surrounded by a continuous basement membrane containing laminin and type IV collagen; however, bullous pemphigoid antigen was either completely undetectable or faint and discontinuous rather than linear. In contrast to this specific defect in bullous pemphigoid antigen found in basal cell carcinoma, well-differentiated superficially invasive epidermal squamous cell carcinoma and several benign epidermal tumors (trichoepithelioma, wart, keratocanthoma, seborrheic keratosis, cylindroma) displayed all three antigens in the basement membrane that surrounded epithelial cell aggregates. Cylindroma displayed in addition, broad areas of type IV collagen in the hyalinized material between epithelial islands. Basal cell carcinoma was the only tumor examined in which there was a specific antigenic defect in the basement membrane. This defect in bullous pemphigoid antigen may be due to abnormal synthesis by the tumor cells and could be related to the absence of differentiation of these cells.