Table 4.
HER2 gene amplification status as defined by HER2 copy number alone, HER2/CEP17 ratio alone, and by algorithms for combined ratio/copy number given in published guidelines (see main paper text for references)
| Category | Amplified by copy number (≥6.0) | Amplified by ratio (≥2.0) | Amplified by ratio and copy number combined algorithm | |||
|---|---|---|---|---|---|---|
| Count of cases (n) | Proportion of cases (%) | Count of cases (n) | Proportion of cases (%) | Count of cases (n) | Proportion of cases (%) | |
| All HER2 IHC categories | ||||||
| ER‐positive | 738 | 10.2 | 1235 | 17.0 | 1414 | 19.5 |
| ER‐negative | 162 | 17.9 | 246 | 27.1 | 274 | 30.2 |
| All | 1328 | 11.0 | 2148 | 17.8 | 2415 | 20.0 |
| HER2 IHC 2+ cases only | ||||||
| ER‐positive | 594 | 9.4 | 1054 | 16.6 | 1204 | 19.0 |
| ER‐negative | 123 | 16.1 | 200 | 26.1 | 225 | 29.4 |
| All | 1066 | 10.1 | 1842 | 17.5 | 2050 | 19.5 |
A total of 12 049 cases were available for analysis when HER2 IHC category was not taken into consideration of which, 10 523 (87.3%) were HER2 2+ by IHC