A rare case of giant congenital melanocytic nevus: its embryological and molecular basis

Congenital melanocytic nevus (CMN) is predominantly distinguished by the presence of nevomelanocytes or nevus cells arranged in well-ordered clusters within the epidermis, as well as organized in the dermis. Giant congenital melanocytic nevus (GCMN) is an uncommon dermal lesion defined by benign proliferative growths of nevomelanocytes that are present at the time of birth. CMNs arise in utero between the 5th and 24th weeks of gestation, attributable to localized genetic anomalies that provoke the excessive proliferation of melanocytes. In individuals with giant CMN, a gain-of-function mutation in the NRAS gene is identified, leading to the aberrant proliferation of embryonic melanoblasts. Previously, elucidation of a murine model for giant congenital nevus demonstrated that both nevi and melanoma exhibit significant expression of Sox10. CMNs represent aggregates of melanocytes situated within the dermis, with varying degrees of extension into subcutaneous adipose tissue, musculature, and peri-adnexal regions. The present report deals with unveiling the embryological and molecular basis of congenital melanocytic nevus.