IHC ER and PR test results are reported using the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) scoring criteria:
- A positive test is defined as positive staining of greater than or equal to 1% of tumor cell nuclei.
- A negative test is defined as staining of less than 1% of tumor cell nuclei.
- Intensity of staining of tumor cell nuclei may be determined by estimation or a quantification method.
- For positive test results, the report includes this estimate of the staining intensity over the entire tumor area of the tissue section. Staining intensity is reported as weak, moderate, or firm.
- The report must include a description of the specimen adequacy for evaluation, the primary antibody clone, regulatory status (IVD/ASR), type and time of fixation (cold ischemia time and total fixation times, to be held within 6 to 72 hours ), decalcification (specimen may be rejected if decalcified using strong acids, since this can affect staining and prevent accurate results), along with the usual required identification and report elements.
- Appropriate positive and negative controls are stained concurrently with the patient slides, ideally on the same slide whenever possible. Status and evaluation of controls must be included within the pathology report. Using internal controls is feasible, as normal epithelial cells will show internal positive or negative reactions for ER and PR.
- The ASCO/CAP synoptic report format is utilized within the report.
Table 3. Allred Scoring of Estrogen and Progesterone Testing by Immunohistochemistry.| Proportion Score | Positive Cell % | Intensity | Intensity Score |
| 0 | 0 | None | 0 |
| 1 | None | Weak | 1 |
| 2 | 1–10 | Intermediate | 2 |
| 3 | 11–33 | Strong | 3 |
| 4 | 34–66 | |
| 5 | 34–66 |
