FOLR2 and neoplasm: As noted in the Introduction, because FRβ is expressed solely on myeloid cells (5, 6) and since its expression in tumor tissues correlates with poor overall survival (5, 30–32) (Supplementary Figure 1), FRβ has become both an important marker for tumor infiltrating TAMs/MDSCs and an intriguing target for receptor-directed therapeutics (4, 6, 7, 9).