Malignant melanoma transformation within a nevus of Ito

The mongolian spot, nevus of Ota, and nevus of Ito are the most common morphologic forms of the dermal melanocytoses, a group of benign pigmented lesions histologically characterized by the presence of melanocytes within the dermis. Nevus of Ito is clinically distinct, presenting with unilateral, bluish gray, patchy discolorations in the skin within the distributions of the posterior supraclavicular and lateral cutaneous brachial nerves. Although all dermal melanocytoses are generally considered benign, rare cases of malignant transformation associated with nevus of Ota have been described. Only one case of malignant melanoma transformation in association with nevus of Ito has previously been reported. We present the second description of malignant melanoma transformation within a nevus of Ito and provide comment on the malignant potential of the dermal melanocytoses. (J Am Acad Dermatol 2010;62:869-74.)