IL17A and esophageal squamous cell carcinoma: Il-17-producing mast cells were found to be densely located in the muscularis propria layer in ESCC and are thought to mediate tumor-protective immunity through the recruitment of effector CTLS, M1 macrophages, NK cells, T cells, and dendritic cells to the tumor site, thus serving as a favorable prognostic factor (164, 165).