Of all SWI/SNF subunit genes, BAF250A/ARID1A is the most commonly mutated gene in human cancers: the gene is mutated in a large proportion of ovarian clear cell cancers (~45%–57%), ~30% of endometrioid cancers, a small proportion of bladder cancers and other tumours.29, 30. This evidence concerns the gene ARID1A and urinary bladder cancer.