Commonly mutated SWI/SNF subunits include SMARCA4 inactivation in undifferentiated thoracic malignancies and small cell carcinoma of the ovary, hypercalcemic type [6, 7] as well as poorly differentiated sinonasal carcinoma [8], SMARCB1 inactivation in epithelioid sarcoma [9, 10], PBRM1 truncating mutations in clear cell renal cell carcinoma [11], and inactivating mutations of members of the ARID family in many different cancer types, including cholangiocarcinoma [12]. The gene discussed is SMARCA1; the disease is cancer.