Diagnosis: Giant congenital nevus
Congenital melanocytic nevi (CMN) are pigmented lesions that are present at birth and created by the abnormal migration of neural crest cells during embryogenesis.1 Nevi are categorized by size as small (<1.5 cm), medium (1.5-20 cm), large (>20 cm), and giant (>40 cm).2 Congenital nevi tend to start out flat, with uniform pigmentation, but can become more variegated in texture and color as normal growth and development continue. Giant congenital nevi are likely to thicken, darken, and enlarge as the patient grows. Some nevi may develop very coarse or dark hair.
CMN can cover any part of the body and occur independent of skin color and other ethnic factors.3 Giant congenital nevi are rare, with an incidence of approximately one in 50,000 live births and with males and females equally affected.3,4 The condition is diagnosed at birth, based on the appearance of the lesions.
The differential diagnosis for CMN includes café au lait macules, blue-gray spots (aka Mongolian spots), nevus of Ota, nevus spilus, and vascular malformations (TABLE).5 CMN may present in almost any location and may be brown, black, pink, or purple in color. Café au lait macules, blue-gray spots, nevus of Ota, nevus spilus, and vascular malformations have individual location and color characteristics that set them apart clinically.
