Bcl-2 and Bax in congenital naevi

Melanocytes represent a static component of the epidermis, and the role of apoptosis in basal melanocyte function and melanocytic tumour formation has not been fully elucidated. The aim of this study was to investigate the expression of Bcl-2 anti-apoptotic and Bax apoptotic proteins in congenital naevi in correlation with p-27 protein and Ki-67 proliferative index. Our material comprised 30 congenital naevi (eight giant) excised from children aged from 15 days to 14 years old. The immunohistochemical streptavidin-biotin method was performed on paraffin sections for the detection of Bcl-2 (cl100/D5), Bax (cl2D2) , Ki-67 (MIB-1) and p-27 (1B4) proteins with monoclonal antibodies. Bcl-2 protein was detected in all cases showing a strong diffuse cytoplasmic expression in > 70% of the naevocytes and was preserved in the deeper parts of the naevi. On the other hand, Bax was detected in 13 of the cases, showing a fainter cytoplasmic expression in 40-50% of the naevocytes without any particular topographic distribution. Ki-67 was detected in all cases showing a limited expression in 1-2% of the nuclei mainly in the junctional and upper dermal components. p-27 protein showed a broad diffuse nuclear expression (> 70% of the nuclei) in all cases with a particular increase in the deeper parts of the naevi. Bcl-2 expression showed a parallel correlation with p-27 protein. Broad Bcl-2 expression in congenital naevi suggests that suppression of apoptosis may play an important role in the maintenance of naevocytes despite the low proliferative activity.