The PUVA-induced pigmented macule: a lentiginous proliferation of large, sometimes cytologically atypical, melanocytes.

Eleven PUVA-induced pigmented macules (PM) obtained from seven psoriatic adults 4 to 6 years after starting PUVA therapy were compared to eight sun-induced pigmented macules (SM) and five specimens of light-protected skin (LPS) from twelve nonpsoriatic control subjects who had not received ultraviolet radiation therapy. Unlike SM, many PM were darkly or irregularly pigmented. In a blind histologic assessment using routine and L-dihydroxyphenylalanine (dopa)-incubated tissue sections, both PM and SM were lentigines. Three of eleven PM had slight melanocytic atypism, compared to none of eight SM. When compared to SM and LPS, PM had a significantly increased proportion of hypertrophic melanocytes. These observations demonstrate that chronic PUVA induces pigmented macules characterized by a lentiginous proliferation of large melanocytes which, in some cases, may be slightly atypical. PUVA-treated individuals require continual monitoring for atypical melanocytic lesions.