To assess HER2 expression in UC, we retrospectively identified 172 tumor samples of advanced UC (upper tract and muscle-invasive bladder cancer [MIBC]) from 162 patients treated at the University of California San Francisco (UCSF) and sequenced using UCSF500 (an institutional sequencing panel) and evaluated their HER2 expression using IHC (Supplementary Methods). This evidence concerns the gene ERBB2 and neoplasm.