Clinical, Genetic and Innate Immunity Characteristics of Melanoma in Organ Transplant Recipients

The aims of this study were to determine the clinical and histological characteristics of melanoma in transplant recipients, the mutation profile (BRAF, NRAS and c-KIT genes), and the immune tolerance of the tumour microenvironment by immunohistochemical study of the expression of indoleamine 2,3-dioxygenase (IDO), PD1, PD-L1, CD8 and FoxP3. The study population comprised patients who had undergone a renal transplant in Nantes University Hospital who developed post-transplantation melanoma. Twenty cases of melanoma out of 4,663 transplant recipients were studied. The results differed from the usual data with respect to melanoma site: 40% were located on the face and were of the malignant lentigo type. The mutation profile was concordant with that of the immunocompetent population. IDO was expressed in all the sections tested, while CD8, FoxP3, PD1 and PD-L1 were poorly expressed. This reflected a highly immunodepressed tumour environment, raising the question of the inductive role of IDO on tumour immune tolerance in patients presenting with long-term immunodepression.