Cutaneous malignant melanoma appearing during photochemotherapy of mycosis fungoides.

We report a case of malignant melanoma that appeared in a 56-year-old man with mycosis fungoides (stage Ia) during treatment with PUVA. The cumulative UVA dose was 1,177 J/cm2. The pigmented lesion was removed and PUVA therapy discontinued. Histological examination revealed a superficial spreading malignant melanoma (1.77 mm thick, Clark level IV). The delayed-type cutaneous hypersensitivity was studied. The presence of a second malignancy after mycosis fungoides and PUVA therapy may have been coincidental. Nevertheless, this case suggests that the immunosuppression induced by mycosis fungoides and by PUVA therapy might be a pathogenetic factor in the development of malignant melanoma.