Congenital Melanocytic Nevi

Excerpt

A congenital melanocytic nevus (CMN) is a skin lesion characterized by benign proliferations of nevomelanocytes and presents at birth or develops within the first few weeks. These lesions may also be referred to as giant hairy nevi, the term conveying the frequent clinical presence of excess hair growth.

CMN are principally classified based on size into small, medium, and large or giant. This is determined by the projected adult size of the maximal diameter of the lesion. Small CMNs are projected to be <1.5cm in diameter, medium 1.5 to 19.9cm, and large or giant >20cm. The scaling factor used to predict adult size is based on anatomical location. CMN located on the head are predicted to grow by a factor of 1.7, on the lower limb 3.3, and upper limb and torso by 2.8. The rationale for classification based on size is due to larger lesions having a higher risk of melanoma, cosmetic implications, more challenging surgical excision, and higher rates of associated symptoms.