Loss of ARID1A, a tumor suppressor gene, has been shown to have significant prognostic value in several malignancies, gastric cancer [103–105], lung cancer [106], hepatocellular carcinoma [107–109], breast cancer [110], osteosarcoma [111], clear cell renal carcinoma [112, 113], and small intestinal carcinoma [114]. The gene discussed is ARID1A; the disease is gastric cancer.