ERBB4 and urinary bladder cancer: Prompted by the finding of common genomic alterations in the region of the NRG1 gene on 8p12 in aggressive bladder cancers and other solid malignancies, as well as the known overexpression of EGFR and ERBB2 in some bladder tumours, we examined the expression of NRG1 mRNA and protein expression of EGFR, ERBB2, ERBB3 and ERBB4 in bladder tumour tissues and cell lines.