Malignant Melanoma Arising in Giant Congenital Melanocytic Nevus: A case report

Kim, Jung Sun; Song, Sang Yong; Song, Kye Yong; Chi, Je G

Abstract

Giant congenital melanocytic nevus is found in 0.1% of live born infants. If present, this lesion has a 6.3% chance to develop malignant melanoma. We report such a case in a 22-year-old woman who had multiple pigmented skin lesions since birth. Rapidly growing masses were recently detected in the 19 cm-sized occipital pigmented lesion. Removed scalp lesion revealed yellowish white lobulated soft nodules in the background of pigmented nevus. Microscopically, the nodules consisted of epithelioid cells with prominent nucleoli, and pleomorphic cells including signetring cells. These cells seldom contained melanin pigment. There were metastatic aggregates of tumor cells in the cervical lymph node, which were reminiscent of germinal centers of lymph nodes. S-100 protein immunostaining was helpful to distinguish them. Incidentally, focally scattered pigmented spindle cells were seen in the capsule of a lymph node