Table 1. Sample classification by IHC results.
| IHC result |
Number of samples N (%) |
Ki67-positive N (%) |
|---|---|---|
| ER | ||
| Negative | 65 (28%) | 63 (97%) |
| Positive | 168 (72%) | 126 (75%) |
| PR | ||
| Negative | 71 (30%) | 67 (94%) |
| Positive | 162 (70%) | 122 (75%) |
| HER2 | ||
| Negative | 183 (79%) | 144 (79%) |
| Equivocal | 13 (6%) | 12 (92%) |
| Positive | 37 (16%) | 33 (90%) |
| Total | 233 | 189 (81%) |
| IHC SUBTYPE* | ||
| Luminal A | 134 (58%) | 96 (72%) |
| Luminal B | 26 (11%) | 23 (88%) |
| HER2-enriched | 11 (5%) | 10 (91%) |
| Triple-negative | 48 (21%) | 47 (98%) |
| Of basal type | 45 (94%) | 42 (93%) |
| Undetermined** | 14 (6%) | 13 (93%) |
* Tumor subtype definitions: luminal A: ER+/HER2-; luminal B: ER+/HER2+; HER2-enriched: ER-/HER2+; triple-negative: ER-/PR-/HER2-; TN of basal type: EGFR+ and/or CK5/6+.
** 14 cases were not assigned a subtype: 13 cases had equivocal HER2 results and no confirmatory FISH; 1 case was ER-/PR+/HER2- with a weak PR positivity.