Evaluation of tissue immunostaining of HLA-G in melanocytic lesions

Melanoma is considered the most aggressive form of skin cancer and develops from the malignant transformation of melanocytes. The expression of the human leukocyte antigen G (HLA-G) molecule is among the immune escape mechanisms of melanoma tumor cells and is related to the stage of the disease, response to treatment, and metastatic status. Therefore, the present study aims to associate the expression of HLA-G with the different histological types of melanoma in tissue samples. Were analyzed forty-six cases of melanocytic lesions of different histological subtypes obtained through surgical resection in the Hospital Universitário Antônio Pedro/EBSERH (CAAE:64852022.1.0000.5243). Immunostaining was performed with the monoclonal antibody 4H84 (Santa Cruz Biotechnologies) and revealed with the GBI-Emerald Chromogen Kit. Immunoreactivity was classified as 0 for the absence of staining, 1 for less than 25% of positive cells, and 2 for more than 25% of positive cells. The 46 cases studied comprised 12 nevi (27,3%) and 32 melanomas (72,7%). The nevi were intradermal (91,7%, n=11) and compound (8,3%, n=1) types. The melanomas were acral lentiginous (8,8%, n=3), superficial spreading (29,4%, n=10), in situ (17,6%, n=6), lentigo maligna (38,2%, n=13) and nodular melanoma (6,0%, n=2). No nevi or in situ melanoma were positive for HLA-G immunostaining, while 6 cases of invasive melanoma (18,8%) were positive. Among these 6 cases, 3 were lentigo maligna melanoma (50,0%), 2 were superficial spreading (33,3%) and 1 was nodular melanoma (16,7%). Analyzing only cases with more than 25% of positive cells (50,0%, n=3), two were lentigo maligna (66,7%), and one was nodular melanoma (33,3%). Despite the low sample size, the results suggest that HLA-G may be present in melanomas with a relatively low frequency. However, when present, it is associated with more aggressive lesions histological subtypes, suggesting its use as a biomarker of disease severity and a possible therapeutic target.