Malignant melanoma in xeroderma pigmentosum: search for a precursor lesion.

Abstract

Malignant melanomas occur with increased frequency and at an early age in patients with xeroderma pigmentosum (XP). The purpose of this study was to describe the histologic features of malignant melanomas in patients with XP and to search for a possible precursor lesion. Clinical records and hematoxylin-eosin-stained sections of 19 malignant melanomas from seven patients with XP were examined. A search was conducted for malignant melanoma precursor lesions (melanocytic nevi and solar lentigines lateral to and contiguous with the malignant melanomas). Basal cell carcinomas removed from the same patients were used as controls. Malignant melanomas were characteristically found in biopsy specimens of small elevations and/or changed color foci arising in large, flat, darkly pigmented, gradually enlarging macules. Histologically, solar lentigo was lateral to and contiguous with malignant melanoma in 88% of the malignant melanomas. Transitional areas were present. A significantly lower number (22%) of contiguous solar lentigines, without transitional areas, were observed in the basal cell carcinoma controls. Most of the invasive malignant melanomas were spindle cell malignant melanomas. We propose that solar lentigo is the most common precursor lesion of malignant melanoma in patients with XP.