Tumor infiltrating lymphocytes in primary melanoma are associated with a better prognosis.

Background: The relationship between tumor infiltrating lymphocytes (TIL) and survival in melanoma is poorly understood. We present a large multicenter study assessing the association between TIL and survival.

Methods: The Sentinel Lymph Node Working Group database was queried from 1993 to 2024 for cases with known TIL and survival data. TIL was analyzed dichotomously and stratified as non-brisk, brisk, and absent. Clinicopathologic factors were correlated with melanoma-specific survival (MSS), overall survival (OS), and recurrence-free survival (RFS).

Results: Among 4957 patients, TIL was present in 3980 (80.2 ​%) of patients. TIL was prognostic of MSS (p ​= ​0.0033), OS (p ​= ​0.0053), and RFS (p ​= ​0.0011). In the stratified analysis, brisk TIL was more strongly associated with MSS, OS, and RFS than non-brisk TIL (all p ​< ​0.04). Among patients with a positive sentinel lymph node, TIL was prognostic of MSS, OS, and RFS (all p ​< ​0.03).

Conclusions: TIL is strongly predictive of survival in melanoma and may be useful in risk stratification when deciding whether risks of adjuvant therapy outweigh benefits for certain patients.