FGL1 and neoplasm: It has been reported four ligands of LAG-3 in tumor microenvironment mainly including galactose lectin-3 (Galectin-3), major histocompatibility complex II (MHC II), fibrinogen-like protein 1 (FGL1), and hepatic sinusoid endothelial cell lectin (LSECtin) (Figure 1). MHC II is the main ligand of LAG-3 (28).