In gastric cancer, ARID1A is frequently mutated in Epstein-Barr virus (EBV)-positive and microsatellite instability (MSI) subtypes/DNA mismatch repair (MMR) protein deficiency characterized by frequent overexpression of PD-L1/L2, CDKN2A methylation, PIK3CA mutations, and rare TP53 mutations2–5. Here, ARID1A is linked to gastric cancer.