The development of two different malignancies in a patient with large congenital melanocytic nevus.

Patients with large congenital melanocytic nevus (LCMN) have a high risk of developing malignant melanoma (MM) and other malignancies. We report a case of a mesenchymal malignancy that best fit the diagnosis of a malignant peripheral nerve sheath tumor and subsequent development of a MM developing from a LCMN. There are no previous reports of a second primary malignant neoplasm arising from a LCMN.