Melanoma Within a Congenital Nevus

A 48-year-old Hispanic man had a tender, bleeding growth within a darkly pigmented plaque on the right flank. The pigmented lesion had been present since birth; it was previously asymptomatic. The tumor arose out of the mainly flat patch 6 months earlier and had slowly enlarged. The patient worked indoors, wore sunscreen daily, and generally avoided outdoor activities. He had no family history of skin cancer.

Results of a comprehensive blood panel obtained about 2 weeks earlier showed elevated levels of cholesterol, triglycerides, and serum glucose.

The friable but hard nodule measured 1.3 3 1.4 cm, and the pigmented plaque measured 5 3 1.6 cm. Biopsies of both the central nodule and the thickest region of the plaque showed malignant melanoma with a maximal thickness of 0.91 mm. On the basis of the history, the melanoma was presumed to be growing out of a congenital nevocellular nevus.

The patient was referred to surgery for wide local excision and to oncology for metastatic evaluation and possible adjuvant interferon therapy.