CMNs

CMNs refers to congenital melanocytic nevi, usually discussed in plural as CMNs when multiple lesions are present; the singular term is CMN. These are pigmented skin lesions that are present at birth or appear shortly afterward, arising from a localized proliferation of melanocytes during fetal development. Most CMNs are benign, though size and other factors influence risk and management.

Clinically, CMNs are categorized by size: small CMN generally under 1.5 cm in diameter at birth; medium CMN roughly 1.5 to 20 cm; and large or giant CMN exceeding about 20 cm. Lesions can be solitary or multiple and may occur anywhere on the body. Giant CMNs, in particular, may involve deeper tissues and can be associated with neurocutaneous melanosis, a condition involving pigmented cells in the brain or spinal cord.

Melanoma risk in CMNs increases with size and certain locations; small CMNs carry a relatively low risk, while large or giant CMNs require careful, long-term surveillance. Management is individualized and may include observation, surgical excision, tissue expansion, or laser treatments. Multidisciplinary care, especially for larger lesions, often involves dermatology, plastic surgery, and, when indicated, neurology.

In clinical practice, CMNs are assessFalse in relation to size, location, age, and potential neurologic involvement. Clear documentation of the number of lesions and their characteristics helps guide monitoring plans and treatment decisions.