To understand which variables may affect this agreement, we subdivided our series and the external validation series into 2 separate groups as follow: (1) 61 and 79 clearly non amplified BC (<4.0 HER2 s/n) as well as 55 and 19 highly amplified BC (≥6.0 HER2 s/n). This evidence concerns the gene ERBB2 and breast cancer.