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ER status is whether the tumour's cells carry the oestrogen receptor, read by staining nuclei. One percent or more of stained nuclei is positive and means hormone-blocking treatment can work; 1 to 10 percent is 'low positive' and behaves more like negative.
The ASCO/CAP 2020 guideline calls a breast cancer ER-positive when at least 1 percent of tumour cell nuclei stain by validated immunohistochemistry, ER-negative below 1 percent, and introduces 'ER low positive' for 1 to 10 percent with a comment that these tumours often behave like ER-negative disease. Every endocrine therapy label (tamoxifen, aromatase inhibitors, fulvestrant) and the CDK4/6 inhibitor, PI3K, AKT and oral SERD labels are written for hormone-receptor-positive or ER-positive disease without restating the 1 percent rule, so the guideline threshold is what laboratories apply. The same 1 percent rule is used for the progesterone receptor.
In plain words · The hormone switch that drives most breast cancers. Blocking or destroying it is the oldest and most effective targeted therapy.
If 1 percent or more of your tumour cells stain for the oestrogen receptor, the cancer is ER-positive and hormone-blocking drugs (tamoxifen, aromatase inhibitors, fulvestrant) are part of treatment, usually with a CDK4/6 inhibitor when the cancer has spread. A result between 1 and 10 percent is 'low positive'; your team may treat it more like ER-negative disease and discuss chemotherapy.
Written only from the label or guideline text cited on this page. Not medical advice; your own report and the reading your team gives it come first.
ER-positive: at least 1 percent of tumour cell nuclei stain positive by IHC. ER low positive: 1 to 10 percent. ER-negative: less than 1 percent or no staining, with internal and external controls behaving as expected.
“ER-positive... if ≥ 1% of tumor cell nuclei are immunoreactive”
ASCO/CAP estrogen and progesterone receptor testing guideline, 2020 update (Allison et al., J Clin Oncol)| Threshold | Drug | Cancer | Regulator | Source |
|---|---|---|---|---|
| ER-positive (guideline >= 1% nuclei) | Elacestrant | HR-positive / HER2-negative breast cancer | FDA | label |
| Hormone receptor-positive (guideline >= 1% nuclei) | Alpelisib | HR-positive / HER2-negative breast cancer | FDA | label |
| Hormone receptor-positive (guideline >= 1% nuclei) | Capivasertib | HR-positive / HER2-negative breast cancer | FDA | label |
Also defined by ASCO/CAP estrogen and progesterone receptor testing guideline, 2020 update (Allison et al., J Clin Oncol).
Matched on the name and aliases of the readout in the title, setting and summary of each trial; a match is a mention, not proof the readout was an entry criterion.
Shares ESR1 mutation (ligand-binding domain, usually in ctDNA), Alpelisib, Capivasertib, HR-positive metastatic breast cancer after CDK4/6 inhibitors and the tag biomarker.
Shares Capivasertib, Endometrial cancer, HR-positive / HER2-negative breast cancer and the tag biomarker.
Shares Capivasertib, Immunohistochemistry (IHC), Endometrial cancer, HR-positive / HER2-negative breast cancer and the tag biomarker.
Shares Immunohistochemistry (IHC), Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag biomarker.
Shares Immunohistochemistry (IHC), Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag biomarker.
Shares Immunohistochemistry (IHC), Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag biomarker.
Shares Immunohistochemistry (IHC), Endometrial cancer and the tag biomarker.
Shares Ribociclib, Letrozole (and other aromatase inhibitors), Abemaciclib, Palbociclib.
Every source this page cites, grouped by who published it. Grouping is read from the web address, not assigned by hand.
A source that has moved or gone is reported by the weekly link check. /audit/