Prognostic Impact of Tumor Immune Microenvironment and Its Predictive Role in Salivary Gland Cancer

Background: Recently, many studies have investigated the role of tumor immune microenvironment (TIME) in carcinogenesis, highlighting its relation to both tumor regression and progression. In particular, the "inflammatory system", made of innate and adaptive immune cells, interacts with cancer cells and their surrounding stroma. In this setting, the aim of this review is to summarize the current literature regarding the TIME of major salivary gland carcinomas (MSGCs), with particular attention on the characteristics and prognostic role of tumor infiltrating lymphocytes (TILs), the mechanisms that lead to TILs exhaustion and the important additional immune infiltrating factors that help SGC progression or remission.

Methods: A comprehensive literature search was performed concerning published articles on the role of TIME in MSGCs.

Results: In this work we summarize the advancing knowledge on TIME in SGCs by demonstrating the key prognostic and/or predictive value of specific immune features.

Conclusion: From the analysis of the current 'status of the art' it clearly emerges a need for precise, unambiguous phenotyping of immune cell populations, as well as a more thorough understanding of the frequencies and interactions of multiple immune cell types inside the TIME and their spatial localization (intratumoral vs. stromal).