ERBB2 and bladder transitional cell carcinoma: Mutations affecting the FGFR signature included genes involved in FGFR activation such as FGFs and genes downstream of the FGFR such as MAPK1&3 and BRAF. The signaling by ERBB2 included mutations directly affecting ERBBRs such as ERBB3&4 and downstream signaling mediators such as AKT1, PIK3CA, and KRAS. The signature of chromatin organization and modifying enzymes included genes relevant for BLCa, such as the ARID1A gene, which controls the gene transcription by modifying chromatin structure and the KMT2D gene, a histone methyltransferase.