Functional cytokine-based classification of tumor-infiltrating lymphocytes in melanoma

Abstract

Tumor-infiltrating lymphocytes (TILs) are important prognostic and predictive biomarkers of melanoma. However, the histological classification of TILs into brisk, non-brisk, or absent categories remains subjective and prone to inter-observer variability. The tumor immune microenvironment (TIME), regulated by cytokines such as tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), plays a central role in tumor progression and therapeutic response. This study investigated whether cytokine immune scoring could serve as a functional adjunct to histological TIL evaluation. A total of 205 early-stage nodular cutaneous melanoma cases from treatment naïve black South African patients were analyzed (65 brisk, 60 non-brisk, and 80 absent). TNF-α and IFN-γ expression were quantified by immunohistochemistry using a modified Allred method and correlated with TIL categories. Three experienced pathologists took part in cytokine immune scoring and any discrepancies were addressed by consensus. Both cytokines were significantly associated with TIL patterns (χ² p < 0.001, Cramér's V ≈ 0.31-0.41), with expression increasing from absent to non-brisk to brisk TILs. Logistic regression revealed 3-4-fold higher odds of high cytokine expression in non-brisk and 6-8-fold higher odds in brisk versus absent cases. The diagnostic metrics indicated moderate sensitivity and specificity but strong negative predictive values. Discordant cases revealed immune activity that was not reflected by morphology alone. These findings support cytokine immune scoring as a complementary tool for refining the functional assessment of the TIME in melanoma.