FOLR2 and renal cell carcinoma: Mujal et al. classified macrophages in the RCC TIME into four subgroups: terminally differentiated C1q c chain (C1QC) + TAMs; TAMs with stress response programs, including selenoprotein P plasma 1 (SPP1), which are less mature than C1Q + TAMs, showing higher monocyte marker levels like S100 calcium—binding protein A (S100A) genes, and lower major histocompatibility complex (MHC)-II gene levels; and TAMs expressing the antioxidant gene SEPP1, similar to C1Q + TAMs but enriched for folate receptor 2 (FOLR2) [240].