ARID1A is frequently mutated in ovarian clear cell carcinomas [9, 10], hepatocellular carcinomas (HCCs) [11, 12], and gastric cancers [4, 6, 13]; ARID2 in HCCs [11, 12, 14]; PBRM1 in renal cell carcinomas [15]; and SMARCA4 in small cell carcinomas of the ovary of hypercalcemic type (SCCOHT) [16–18]. The gene discussed is ARID1A; the disease is hepatocellular carcinoma.