TP53 and gastric cancer: This subtype can also express PD-L1 and may respond to immune checkpoint inhibitors.80,81 Chromosomal unstable GC (CIN GC) are characterized by frequent mutations in the tumor suppressor gene TP53, which is also the most frequently altered gene in all GC.77 CIN GC often contains amplifications of genes encoding plasma-membrane bound receptors that present actionable targets, such as EGFR, FGFR2, HER2, and MET.82 Genomically stable GCs predominantly show a diffuse histological phenotype.