PDCD1 and neoplasm: Next, others phagocytosis checkpoints including PD-L1-PD-1 axis (in 2017) [40], major histocompatibility complex class I (MHC-1)-leukocyte immunoglobulin-like receptor subfamily B member 1(LILRB1) axis (in 2018) [41], cluster of differentiation 24(CD24)-sialic acid binding Ig like lectin 10(Siglec-10) (in 2019) [42], cluster of differentiation 22 (CD22) (in 2019) [43], signaling lymphocytic activation molecule family 3/4 (SLAMF3/4) (in 2022) [44] and ganglioside 2 (GD2)-sialic acid binding Ig like lectin 7 (Siglec-7) (in 2022) [45] were followingly demonstrated in the tumor microenvironment.