Periocular congenital melanocytic nevi.

Large congenital melanocytic nevi (CMN) are cutaneous malformations of neural crest origin that have a notorious reputation because of their reported propensity to undergo malignant degeneration. Traditionally, complete surgical excision has been advocated based on the premise that large CMN are a precursor to melanoma. Two cases of large periocular CMN are reported to emphasize the importance of distinguishing them from other congenital skin lesions. Data from the literature support the contention that these pigmented skin lesions spawn malignancies and that prophylactic therapy may be indicated.