Malignant melanoma in stasis dermatitis.

Two cases of malignant melanoma arising in established stasis dermatitis are described. One case was clinically thought to be melanocytic whereas the other was not. Histologically, both showed similar features with background varicose change of epidermal atrophy, sloughing of the epidermis, intense proliferation of small thick walled blood vessels, lymphocytic infiltrate and dermal fibrosis. In the superficial aspects of the biopsies there was little clue to the diagnosis of melanoma. In the deeper aspects of case 1, groups of melanocytes were present in the reticular dermis which mimicked benign naevus cells. S-100 protein staining confirmed the melanocytic nature of these lesions, their extent and the epidermal involvement. The latter features supported a malignant diagnosis. These lesions can be overlooked clinically as well as histologically.