Tumor-infiltrating lymphocytes predict sentinel lymph node positivity in patients with cutaneous melanoma

Tumor-infiltrating lymphocytes (TILs) are considered a manifestation of the host immune response to tumor, but the influence of TILs on outcome remains controversial. Studies evaluating the prognostic significance of TILs were published before routine examination of draining lymph nodes by sentinel lymph node (SLN) biopsy, the most important predictor of survival in patients with melanoma. The prognostic implications of TILs were re-evaluated in a large group of patients undergoing SLN biopsy at our institution.

All patients who underwent SLN mapping for primary cutaneous melanoma between January 1996 and July 2005 were evaluated. Univariate and multivariate analyses were performed to assess factors that predict SLN positivity and survival. Factors analyzed included Breslow thickness, ulceration, anatomic site, sex, Clark level, age, mitotic rate, and the presence (brisk or nonbrisk) or absence of TIL.

Eight hundred eighty-seven patients underwent SLN mapping, and a SLN was identified in 875 patients (98.8%). The SLN was positive for tumor in 156 patients (17.6%). Multivariate analysis revealed that only Breslow thickness (P < .0001), ulceration (P = .0004), male sex (P = .03), and absent TILs (P = .0003) were independently predictive of the presence of SLN metastases. In melanomas with a brisk TIL infiltrate, the probability of a positive SLN was 3.9% as compared with 26.2% for melanomas in which TILs were absent. TILs were not an independent predictive factor for survival.

The absence of TILs, together with increasing Breslow thickness, presence of ulceration and male sex, predicts SLN metastasis in patients undergoing SLN biopsy for primary cutaneous melanoma.