As FOLR2+ macrophages were revealed to be embryonic-origin tissue-resident macrophages (TRMs, also known as Kupffer cell-like phenotypes in the liver) (50), it was implied that, during tumor progression, SPP1+ macrophages increased from the infiltration of circulating monocytes, accompanied with reduced FOLR2+ TRMs. Here, FOLR2 is linked to neoplasm.