A significantly lower mRNA expression level of HER3 (P=0.0003), HRG2α (P=0.0159), HRG2β (P=0.0007) and HRG4 (P<0.0001) was observed in muscle-invasive (T2–T4) tumours as compared to superficial (Ta) tumours. The gene discussed is ERBB3; the disease is neoplasm.