bcl-2 expression in melanocytic nevi. Insights into the biology of dermal maturation

Recently, a new category of oncogenes has been discovered that regulate programmed cell death. The bcl-2 oncogene has been found to inhibit cellular death without affecting cellular proliferation. In the skin, bcl-2 expression is limited to cells along the basal cell layer. However, we also noticed that resting melanocytes appeared to express bcl-2. We examined the expression of bcl-2 and its possible role in the biology of benign melanocytic proliferations. Routine paraffin sections of formalin-fixed tissue were labeled with anti-bcl-2 monoclonal antibody, and expression of bcl-2 was detected by a biotin-avidin-immunoperoxidase procedure.

We examined 13 congenital, 11 acquired, and six atypical or dysplastic nevi for expression of bcl-2. Expression of bcl-2 was observed in 11 of 13 congenital nevi. All 11 acquired nevi and 6 nevi with architectural disarray and cytologic atypia expressed bcl-2. Both junctional and intradermal melanocytes expressed bcl-2 in a perinuclear and cytoplasmic pattern. Within neurotized areas, bcl-2 became significantly weaker and totally absent.

In mature tissues, bcl-2 expression is quite limited. It appears to be restricted to pluripotential stem cells that serve as a reservoir for tissue that is constantly undergoing renewal, such as the hematopoietic cells and the intestinal mucosa. In the skin, bcl-2 expression has been previously reported to be limited to the epidermal basal cell layer and proliferation zones. Our results indicate that resting melanocytes and melanocytic nevi regularly express bcl-2.