The somatic genetic events that drive breast cancer have now been well described [3], with multiple clinical trials underway directed against somatic genetic events such as mutation of PIK3CA. Testing for such mutations is likely to become part of routine practice, which will require routine extraction of DNA, and this emphasizes the potential utility of robust DNA based assays of HER2 amplification status, through accurate quantification of HER2 gene copy number in extracted DNA. The gene discussed is ERBB2; the disease is breast carcinoma.