ARID1A and urinary bladder cancer: The development of bladder cancer is linked to the emergence of oncogenic mutations and genetic changes in normal cells [3], and mutations in chromatin regulators (KDM6A, KMT2D, KMD2C, CREBBP and EP300), and AT‐Rich Interactive Domain‐containing protein 1A (ARID1A) are common [2], more than 65% of patients with non‐muscle‐invasive bladder cancer have been found to have inactivation of one or more of these regulators, with ARID1A mutations being more common in T1 stage tumours [4].