Immune cells in the melanoma microenvironment hold information for prediction of the risk of recurrence and response to treatment.

Melanoma is an immunogenic tumor and immunotherapy treatment has established an increase in disease-free and overall survival in melanoma patients. However, a complex network of immunosuppressive mechanisms has been demonstrated to occur at the tumor site and in locoregional immune districts, such as sentinel lymph nodes (SLNs). The interplay between tumor cells and the local microenvironment leads to a tumor-driven shaping of the immune response that results in a heterogeneous cellular and molecular composition of tumor infiltrating lymphocytes (TILs). Several studies have reported the potential prognostic value of TILs infiltrating primary tumors and the association of 'immune signature' in SLNs and in melanoma metastases with prognosis and responsiveness to immunotherapeutic approaches. However, a systematic and deeper characterization of the local immunological status of TILs and SLNs is still required to refine melanoma stage classification.