In addition, mast cells can induce an immunosuppressive tumor microenvironment [17] by directly enhancing regulatory T cell (Treg) function via mast cell-T cell contact [44], IL-10 [46], tryptophan metabolism [47], amphiregulin production [48], or adenosine [44], or indirectly by inducing tolerogenic dendritic cells [5]. This evidence concerns the gene AREG and neoplasm.