Coexistence of regression and tumor infiltrating lymphocytes is associated with more favorable survival in melanoma

Purpose Melanoma is one of the highly immunogenic malignancies, and histological regression (HR) and tumor infiltrating lymphocytes (TILs) represent early signs of activation of the immune system against primary melanoma. In this study we aimed to investigate the potential roles of HR and TILs on survival, as combined or separately. Methods A total of 916 cutaneous melanomas were analyzed retrospectively. Results Only minority of the lesions had HR (25.1%) and they were associated with males ( p = 0.002), axial localization ( p = 0.0001), non-nodular histopathology ( p = 0.0001), thin Breslow depth ( p = 0.01) and nevus-associated melanoma ( p = 0.03). Those with TILs (48.4%) were found in association with lower Clark levels ( p = 0.003), thin tumor thicknesses ( p = 0.001), lower mitotic rates ( p = 0.02), BRAF mutation ( p = 0.03), absence of neurotropism ( p = 0.03), involvement of lymph node ( p = 0.0001) and relapse of disease ( p = 0.04). A significant relationship was found between HR and TILs ( p = 0.01). TILs were independently associated with favorable RFS ( p = 0.02), whereas no relationship was observed between HR and RFS ( p = 0.2). A marked favorable survival advantage was noted in the group with HR (+)/TILs (+) compared to other groups with HR (−)/TILs (−) ( p = 0.007), only HR (+) and only TILs (+). Both HR ( p = 0.05) and TILs ( p = 0.04) were correlated with favorable OS rates. Moreover, HR (+) /TILs (+) patients had more favorable OS than other groups with HR (−)/TILs (−) ( p = 0.002), only HR (+) and only TILs (+). Conclusion Only HR (+) and only TILs (+) subgroups separately were found to be associated with favorable survivals in melanoma. Furthermore, coexistence of HR and TILs, HR (+)/TILs (+) subgroup, had more favorable survival rates compared to only HR (+) and only TILs (+) subgroups.