As a pilot study, we sought to investigate the potential clinical utility of measuring HER2 protein receptors with PID testing in a cohort of 34 HER2-positive (defined by IHC and/or ISH analysis) breast cancer patients, who had undergone trastuzumab-based neoadjuvant therapy, to see if the quantitative measurement of HER2 protein receptors correlated with pathologic response to therapy. The gene discussed is ERBB2; the disease is breast cancer.