Malignant melanoma developing from an intradermal nevus.

A 58-year-old man presented a black nodule with satellites located in the left upper region of the umbilicus. Clinical history and microscopic findings led us to diagnose it as a malignant melanoma developing from an intradermal nevus. Histopathologically, melanoma cells developed upward from the nest of the intradermal nevus and no junctional activity was shown. Cases of malignant melanoma arising from an intradermal nevus have rarely been reported. Moreover, previously reported cases showed melanoma cells beneath the intradermal nevus.