Bladder cancer can be distinguished into two molecular subtypes — luminal or basal — based on their gene expression signature. The luminal subtype has an expression pattern similar to the superficial and intermediate layers of the normal urothelium, with upregulation of PPARγ target genes and enrichment of mutations in FGFR3, ELF3, CDKN1A, and TSC1. Basal tumours have gene expression patterns similar to the basal layer of the urothelium, with upregulation of p63 target genes and enrichment of mutations in TP53 and RB1. Subtype identification can be achieved with 90% accuracy by immunohistochemically assessing GATA3 and KRT5/6 expression, which are markers for luminal and basal subtypes, respectively.