Intralesional interferon alfa-2b in the treatment of basal cell carcinoma. Immunohistochemical study on cellular immune reaction leading to tumor regression.

Four patients with basal cell carcinomas were treated with intralesional injections of interferon alfa-2b (1.5 million IU per injection) three times a week for 2 weeks. Histopathologic examination of biopsy specimens of the lesions confirmed the absence of basal cell carcinoma in all cases 4 weeks after completion of therapy. A dense mononuclear cell infiltrate and numerous ectatic blood vessels were present in the dermis at the sites of previous basal cell carcinoma. Immunohistologic analysis of the dermal infiltrate revealed a marked increase of Leu-4+ T cells with a slight predominance of Leu-3+ helper/inducer T cells over Leu-2+ suppressor/cytotoxic T cells. Most of the dermal infiltrate expressed HLA-DR antigen. In addition, Leu-11+ natural killer cells were observed in the dermal infiltrate. Immunohistologic changes in the skin lesions at the sites of previous basal cell carcinoma suggest that intralesional interferon alfa-2b acts on tumor cells by enhancement of local T-cell-mediated immune responses.