Melanoma arising in a hairy nevus spilus.

Cutaneous melanoma may develop de novo on normal skin or in contiguity with a potential melanocytic precursor. We report a 45-year-old man who presented with a recently developed nodule in a previously stable congenital nevus. Physical examination revealed a 10x18-cm lesion with speckled lentiginous pigmentation and terminal hairs on the lower back. A 2x2-cm suspicious nodule in the lesion was noted by the patient 2 months earlier. Histopathological evaluation of the nevus and the suspicious nodule revealed the characteristics of a melanocytic nevus and melanoma, respectively. It was interesting for the authors to observe terminal hairs in a lesion that was clinically 'speckled lentiginous' in appearance. This case report is a reminder that there may be great variation in the clinical appearance of nevus spilus, and thus dermatologists must be aware of these lesions as potential precursors of malignant melanoma.