A clinical histologic, and immunologic study of a case of metastatic malignant melanoma undergoing spontaneous remission.

A patient with biopsy-proven dermal recurrent malignant melanoma who refused therapy, and who was observed to undergo clinical regression during the period of November 1972 through June 1974 was studied to define the histologic features of spontaneous remission, and to evaluate the immune response as measured by in vitro assays of lymphocyte cytotoxicity and serum effects during the course of regression. Biopsy of regressed areas showed the following histologic features: 1) absence of malignant melanoma cells in basal layers of epidermis with relative increase in basal layer clear cells; 2) dermal inflammatory reaction with lymphocytic infiltrate, melanophages, and degenerate malignant melanocytes; and 3) dermal reactive vascular proliferation and interstitial edema progressing to reparative dermal fibrosis. Using a microcytotoxicity assay with two established allogeneic melanoma cell cultures as target cells, a statistically significant (p less than 0.01) increase in lymphocyte cytotoxicity values was observed over the clinical time course of regression. No significant serum cytotoxic or serum blocking effects were detectable. These findings are consistent with an immunologic basis for the spontaneous remission of the dermal melanoma metastases present in this patient.