With mutations in genes encoding SWI/SNF subunits, including ARID1A, ARID1B, ARID2, PBRM1, SMARCA4, and SMARCB1, collectively occurring in ~20% of all tumor types, SWI/SNF complexes are the most commonly mutated chromatin modulators in human cancer [3]. The gene discussed is ARID1A; the disease is cancer.