TREM2 and hematoma: A critical step in hematoma clearance involves the phagocytosis of extravasatederythrocytes by brain-resident microglia and infiltrating macrophages [13].Erythrocytes exhibit both pro-phagocytic and anti-phagocytic signals on surface.The phagocytic clearance of erythrocytes by microglia/macrophages is regulatedthrough four main pathways: the TAM receptor-growth arrest-specific protein 6(Gas6)/protein S (Pros1)-phosphatidylserine (PtdSer) pathway, the CD36-oxidizedPtdSer pathway, the TREM2-PtdSer pathway, and the SIRPα-CD47 pathway(Fig. 1).