Molecular diagnosis of a benign proliferative nodule developing in a congenital melanocytic nevus in a 3-month-old infant.

Small and intermediate congenital melanocytic nevi have a lifetime risk of developing melanoma estimated to range from 0% to 5%. Secondary benign melanocytic proliferations commonly arise in congenital melanocytic nevi; however, some are difficult to definitively distinguish from malignant melanoma based on clinical features and conventional histology. Herein, we describe the use of comparative genomic hybridization in supporting the diagnosis of a deep penetrating nevus developing within a congenital melanocytic nevus of a 3-month-old infant.