THE PATHOLOGY OF BENIGN MELANOCYTIC NEVI OF THE SKIN WITH SPECIAL REFERENCE TO THEIR MALIGNANT POTENTIAL

Abstract

In this thesis, the pathology of benign melanocytic nevi has been reviewed. The review included; the definition, epidemiolog histogenesis, classification, clinical features, histopathology and malignant potential. Special attention has been paid towards the risk of the development of malignant melanoma on top of benign melanocytic nevi (malignant potential).

Definition: Several names are given to nevi compnsmg; benign melanoma, pigmented mole, pigmented nevus, nevocellular nevus and melanocytic nevus. On the other hand, melanocytic nevi can be put in a midsituation between malformation, and neoplasia.

Epidemiology: Congenital melanocytic nevi are present in 1% of newborn babies, and more frequent in older children and adults. In some reports, the melanocytic nevi are commoner in males than females and in others, the incidence is equal for males and females. Melanocytic nevi tend to be commoner in the extremities of females and in the back of males.

Histogenesis: One hypothesis says that nevomelanocytes in the epidermis and upper dermis are derived from epidermal melanocytes, and nevomelanocytes in lower dermis are derived from the Schwann cells (a dual origin). Another hypothesis posulates. that the nevomelanocytes in the dermis are derived from epidermal melanocytes that drop to the dermis.