Abnormal FGFR signaling directly contributes to tumor development by stimulating cancer cell growth and angiogenesis.74 A wide variety of cancers harbor FGFR aberrations with UCs being the most common at a rate of 32%75 and the most common FGFR aberrations in UCs are mutations (18.3%); followed by copy number amplifications (8.7%) and translocations (7.1%).75 Detection of genetic alterations involving the FGFR3 gene (mutations or gene fusions) provides guidance to predict response to FGFR inhibitors. The gene discussed is FGFR3; the disease is cancer.