Benign melanocytic lesions. A morphometric analysis.

Nuclei of melanocytes in 10 lentigines simplices, 10 junctional, 10 compound and 10 intradermal acquired melanocytic nevi were morphometrically evaluated, at three different skin levels: epidermis, papillary and reticular dermis. The considered parameters were: area, perimeter, form Ar, and form Ell. Mean values of nuclear area and form Ell demonstrated a progressive increase from lentigines to junctional to compound to dermal nevi. This trend was also observed for each considered level. In compound nevi mean values of nuclear area showed an increase from the epidermis to the papillary dermis. In compound and intradermal nevi they showed a decrease from the papillary to the reticular dermis. Mean values of nuclear form Ell presented a continuous increase from the epidermis to the papillary and reticular dermis. Our study shows that, in the evolution of the considered melanocytic lesions (from lentigo to dermal nevi), the nuclei of melanocytes become larger and rounder. In compound nevi, epidermal nuclei were smaller and more elongated than those of the papillary dermis. In compound and intradermal nevi, superficial dermal nuclei appeared larger but less round than the deep ones. These peculiar findings have been generally referred to as a melanocytic maturation process. They are also probably due to other factors, perhaps local factors, because a similar trend is observed in some malignant melanomas.