These findings suggest that ERBB2 amplification and mutation is often a later event in urothelial cancer pathogenesis and not present in all tumor cells in a significant minority of patients with urothelial cancer, which contrasts with breast cancer, a disease in which ERBB2 amplification has been shown to be an early initiating event and highly concordant between primary and metastatic disease sites42,43. This evidence concerns the gene ERBB2 and metastatic neoplasm.