Giant nevi: a review.

Congenital nevi are benign neoplasms that are present at birth and composed of nevomelanocytes. Approximately 1-3% of all newborns have congenital pigmented nevi, and the number of nevi increases with age, peaking by late adolescence to 20-40 nevi in an individual. Giant congenital nevi are often defined as nevi that are greater than 20 cm in diameter in an adult, or nevi that occupy 2% or more of the body surface area. Histologically, nevi are transformed melanocytes, which are normally highly dendritic cells interspersed among basal keratinocytes. The genetic basis of these lesions is not known. Findings of a culture of melanocytes from such a lesion from a showed chromosome rearrangements involving 1p,12q, and 19p. The giant nevi might be associated to several diseases: neurocutaneous melanosis, diffuse lipomatosis, structural brain malformations, hypertrophy of skull bones, limb atrophy, skeletal asymmetry involving both soft tissue hyper-and hypoplasia, von Recklinghausen's disease and vitiligo. The risk of malignant change in giant nevi is probably the most contentious issue in its management. The consensus is that lesions are pre-malignant, but the purported incidence of malignancy varies wildly from 0-42%. Surgical excision remains the mainstay of treatment for large congenital melanocytic nevi, and most giant nevi are managed by staged excision and resurfacing with skin grafts or tissue expanders and flaps.