Aiming to investigate the role of the recently discovered molecular subtypes of bladder cancer in urothelial CIS, we analyzed luminal and basal marker expression using an established surrogate immunohistochemistry (IHC) panel comprising the luminal markers CK20, GATA3, human epidermal growth factor receptor type 2 (Her2), and estrogen receptor (ER) β as well as the basal markers CK5/6 and CK14 in 156 CIS tissue samples from 132 patients. Here, ESR1 is linked to urinary bladder cancer.