Because FRβ, an isoform of FR that is only expressed on myeloid cells (31), is known to exist in both a folate binding and nonbinding state, and since it converts from its nonbinding to folate binding state following macrophage infiltration into solid tumors (or sites of inflammation) (32–34), we wondered whether FRδ might similarly convert from a nonbinding to binding state following Treg migration into a tumor mass. This evidence concerns the gene FOLR2 and neoplasm.