To test whether the two immunohistochemical markers (GATA3 and KRT5/6) could be used for the molecular classification of bladder cancer in daily pathology practice, we performed immunohistochemical stains for GATA3 and KRT5/6 on regular FFPE routine histologic tissue sections (n = 74) that were matched to the original MDACC cohort of fresh frozen tissue samples in which the molecular subtypes were assessed by mRNA expression levels. The gene discussed is GATA3; the disease is urinary bladder carcinoma.