Malignant Melanoma Arising in a Prolific Nevus Sebaceus With Colonization of Trichoblastoma.

Nevus sebaceus (NS) is a cutaneous hamartoma typically found on the head and neck, with a prevalence of 0.3% in newborns. Most NS are quiescent; however, benign and malignant lesions have been reported to arise within these nevi. Malignant transformation is not common but mainly includes basal cell carcinoma and squamous cell carcinoma. Malignant melanoma arising in NS is exceedingly rare, with only 2 previously documented cases. In this article, we report the first case of malignant melanoma arising in a NS in a 68-year-old man in the United States.