Evaluation of tumor infiltrating lymphocytes in cutaneous and uveal melanomas; A histopathological and immunohistochemical study

Introduction: Cutaneous melanoma and uveal melanoma are derived from melanocytes with the same embryonic origin; however, their etiopathogenesis is very different. The presence of tumor-infiltrating lymphocytes (TILs) in melanoma is a kind of host’s antitumor immunological response; however, the associations between the number of TILs and histopathological characteristics and tumor progression remain controversial. Objectives: This study aimed to study the histological characteristics and immunophenotyping of both cutaneous and uveal melanoma affecting Egyptian patients where the melanoma is uncommon. Also, we tried to find the relationship between TIL amount and the tumor progression. Patients and Methods: This is a cross-sectional study to assess the number (amount) and phenotype of TILs in 40 patients with cutaneous melanoma and seven patients with uveal melanoma using immunohistochemistry. Results: The mean age of the cutaneous and uveal melanoma was 58.5±15 and 54.5±15 years, respectively, with no sex predominance. Tumor stage in cutaneous melanoma is associated with a decrease in TIL, whereas uveal melanoma has the opposite effect. The infiltrate was predominantly positive for CD3 and CD8, with minimal expression of natural killer (NK) cell markers. There is a significant difference between TIL and nodal metastasis in both types. Conclusion: In this study we found an association between TIL amount and the tumor stage in both cutaneous and uveal melanomas with a significant difference between TIL infiltration and nodal metastasis. However, correlations between TILs and tumor progression should be further studied in different kinds of melanoma to aid in risk assessment and the prognostic significance of TILs in the rare eye tumor, uveal melanoma.