ERBB2 and breast cancer: According to Ballard [14], the “non classical” amplified cases include (1) low amplified BC with a ratio ≥ 2.0 and an average HER2 copy number between 4.0 and 5.9, (2) co-amplified BC with a ratio < 2.0, but an average HER2 copy number ≥ 6.0, (3) monosomy-like BC with a ratio ≥ 2.0, but an average HER2 copy number < 4.0, (4) heterogeneous BC presenting clusters of amplified tumor cells (>10%) associated with clusters of non amplified tumor cells [11, 14].