Tumor Infiltrating Lymphocytes in Different Stages of Malignant Melanoma and Correlation with Tumor Stage and Other Prognostic Factors: A Retrospective Multicenter Study

Background: Melanoma is one of the most immunogenic tumors that causes a significant immune response. Tumor infiltrating lymphocytes are an important part of this response. Tumor infiltrating lymphocytes are lymphocytes in close association with tumor cells that have infiltrated tumor nests. In this study, we attempt to evaluate the relationship of tumor infiltrating lymphocytes in malignant melanoma with histopathologic findings, tumor stage, and other prognostic factors. Method: This was a retrospective cross-sectional study. We re-evaluated patients’ specimens and categorized the tumor infiltrating lymphocytes as grades ۰, ۱, ۲, or ۳ based on density and distribution of the infiltrating lymphocytes. Results: We enrolled ۱۱۱ patients with a mean age of ۵۹.۳۳±۱۴.۶۸ years, and a male to female ratio of ۱.۰۹. There was no evidence of tumor infiltrating lymphocytes in ۱۷.۱% of patients. The melanoma subtypes had the following tumor infiltrating lymphocyte grades: ۱ (۴۷.۷%), ۲ (۲۸.۸%), and ۳ (۶.۳%). Cancer stage significantly decreased with increasing grade of tumor infiltrating lymphocyte (P<۰.۰۰۱). Although numerous histopathologic findings had a relationship with tumor infiltrating lymphocytes, only microsatellitosis had a significant relation after adjustments for melanoma stage (P< ۰.۰۰۱). Conclusion: Increased density of tumor infiltrating lymphocytes can show a more effective immune response against melanoma. This response can limit cancer progression and result in tumor diagnosis at lower stages of the disease.