The immune response to melanoma is manifested locally by tumor-infiltrating lymphocytes (TILs). Men and women are known to have varying patterns of immunity, yet sex-specific prognostic implications of TILs have not been explored.

Patients with clinically localized primary melanoma ≥0.76mm in Breslow thickness who underwent sentinel lymph node (SLN) biopsy at our institution were identified. Association between TILs (absent, nonbrisk, and brisk) and SLN positivity was evaluated using logistic regression. Overall survival (OS) was evaluated by TILs status and sex.

Among 1,367 patients identified, 794 were men. TILs were brisk in 143 lesions, nonbrisk in 903, and absent in 321, which did not vary by sex (p=0.71). SLN positivity was associated with TILs among men (brisk 3.8%, nonbrisk 16.9%, absent 26.6%, p<0.001). In contrast, there was no association between SLN positivity and TILs among women (p=0.49). Interaction between brisk TILs and sex on SLN positivity was significant (p=0.029). Among men, presence of brisk TILs was associated with prolonged OS (p=0.038) but not after adjustment for SLN status (p=0.42). There was no association between TILs status and OS among women.

Findings from this single-institution study have yet to be validated by other research groups.

The implications of TILs in predicting SLN positivity appear to be more relevant for men than women.