ERBB2 and cancer: Several authors have reported a higher frequency of HER2 over expression in ductal carcinoma in situ (DCIS) compared with invasive cancer [19,20] Similarly, Liu et al [20] have observed HER2 overexpression as determined by gene amplification using polymerase-chain reaction (PCR)-based techniques in 48% of in situ carcinomas compared with 21% of stage II invasive breast tumours.