Congenital plantar melanocytic nevus with satellite lesions

We report a case of a congenital melanocytic nevus accompanied by a mucous cyst and satellite pigmented macules on the undersurface of the left great toe in a 17-year-old Japanese man. Myxoid change was confirmed by the discharge of viscous liquid when conducting biopsy of the tumor. Besides such an unusual clinical feature of the tumor, accompanying satellite lesions led us initially to consider the possibility of malignant melanoma. However, a biopsy specimen obtained from the tumor revealed the typical features of intradermal type melanocytic nevus. In a specimen obtained from the satellite pigmented lesion, there was a small mass of nevus cells underneath the basement membrane zone, suggestive of having originated from the spread of nevus cells through lymphatic vessels.