A study of large congenital melanocytic nevi and associated malignant melanomas: review of cases in the New York University Registry and the world literature.

BACKGROUND: Patients with large congenital melanocytic nevi (LCMN) are at greater risk for the development of malignant melanoma (MM) than are persons in the general population.
OBJECTIVE: Our purpose was to identify the clinical features of LCMN in those patients in whom MMs actually developed.
METHODS: The records of 117 patients in the New York University Registry of LCMN and the reports of 172 cases of LCMN in the world literature were studied.
RESULTS: Of the 289 cases of LCMN studied, 34 patients (12%) had primary cutaneous MMs within their nevi; in two additional patients, MMs developed at cutaneous sites other than within their nevi. All patients in whom MM developed within LCMN had nevi in axial locations; however, 91% of the LCMN were axial. No MM was found that had arisen in any of the 26 LCMN confined to the extremities. In addition, no MM was found that had arisen in thousands of satellite nevi.
CONCLUSION: When MM develops within an LCMN, it generally does so in those LCMN in an axial location. The absence of cases of MM arising in LCMN confined to the extremities suggests that such nevi represent lower risk lesions, but the number of extremity nevi analyzed was too small to allow definitive conclusions. A striking finding was the absence of MMs arising in satellite nevi.