Local immune response in basal cell carcinoma: characterization by transmission electron microscopy and monoclonal anti-T6 antibody.

We examined lesional and perilesional skin from nine basal cell carcinomas occurring in six patients to determine the role of local immunity in the pathogenesis of these neoplasms. Marked hyperplasia of Langerhans cells and indeterminate cells as defined by monoclonal anti-T6 antibody was observed in lesional and perilesional skin of most specimens. Ultrastructurally, Langerhans cells were observed in the dermis and above the basement membrane zone where mitotic activity was documented. Apposition of Langerhans cells and indeterminate cells with degenerating and necrotic neoplastic keratinocytes and with exocytotic lymphocytes was frequently encountered. Zonal necrosis of carcinoma cells was often immediately peripheral to exocytotic lymphoid cells. These observations support the contention that an active local immunologic response is related to the biologic behavior of some basal cell carcinomas.