Evaluation of expression of genes CADM1, TWIST1 and CDH1 by immunohistochemestry in melanocytic lesions

Malignant melanoma is an aggressive disease and its incidence is increasing worldwide. Genetic predisposition and exposure to environmental factors, especially sunlight, are risk factors. Histopathologic distinction between nevi and melanomas can be difficult. It is anticipated that the evaluation of the immunohistochemical expression of some genes could contribute to the differential diagnosis of questionable histologically lesions. The objective of this study was to investigate wether the evaluation of the immunohistochemical expression of genes CADM1, TWIST1 and CDH1 (E-cadherin), that take part in mechanisms of cell adhesion and epithelial-mesenchymal transition, contributes to the differential diagnosis of melanocytic lesions difficult to diagnose. Retrospective cross-sectional study based on immunohistochemistry analysis of samples of 30 dysplastic compound melanocytic nevi, 30 melanomas less than 1.0mm thick and 30 melanomas more than 1.0mm thick, diagnosed between 2013 and 2016. A score was used to evaluate color intensity and percentage of cells stained. There were significant reductions in the expression of the genes CADM1 and CDH1 in melanomas (below and above 1.00mm of thickness) and in melanomas more than 1.0mm thick, respectively, compared to dysplastic compund melanocytic nevi. There was also lower expression of the genes CADM1 and CDH1 in melanomas greater than 1.0mm thick compared to melanomas less than 1.0mm. The gene TWIST1 showed no significant difference in expression between groups. These findings allow us to conclude that the immunohistochemical expression of CADM1 has the potential to contribute as an auxiliary tool to the differential diagnosis between nevi and melanomas.