Our class C tumours mostly fall (20 of 24; 83%) within UROMOL classes 1 and 3; our class C and UROMOL classes 1 and 3 are characterised by FGFR3 mutations and/or high FGFR3 gene expression and low tumour grade/stage (Fig. 4A). The gene discussed is FGFR3; the disease is neoplasm.