{"entity":{"id":"er-status","kind":"biomarker","name":"ER status (oestrogen receptor by IHC)","aka":["ER status","ER-positive","ER positive","ER+","ER-negative","estrogen receptor status","oestrogen receptor status","ER low positive","ER >= 1%","ER 1-10%"],"tldr":"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.","summary":"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.","asOf":"2026-09-23","links":[{"label":"ASCO/CAP estrogen and progesterone receptor testing guideline, 2020 update (Allison et al., J Clin Oncol)","url":"https://doi.org/10.1200/JCO.19.02309"}],"tags":["biomarker","hormone-receptor"],"related":["pr-status","ki-67-index","esr1-mutation-ctdna"],"cancers":["breast-hr-positive","breast-cancer","hr-positive-early-high-risk","hr-positive-metastatic-post-cdk46","endometrial"],"sections":[],"technologies":[],"targets":[],"drugs":["tamoxifen","letrozole","fulvestrant","palbociclib","ribociclib","abemaciclib","elacestrant","alpelisib","capivasertib"],"companies":[],"institutions":[],"pathways":[],"terms":["hormone-receptor-status","ihc","serd"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"estrogen-receptor","measurement":"ihc-score","scoringRule":{"text":"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.","quote":"ER-positive... if ≥ 1% of tumor cell nuclei are immunoreactive","source":"https://doi.org/10.1200/JCO.19.02309","sourceLabel":"ASCO/CAP estrogen and progesterone receptor testing guideline, 2020 update (Allison et al., J Clin Oncol)"},"thresholds":[{"value":"ER-positive (guideline >= 1% nuclei)","drugId":"elacestrant","cancerId":"breast-hr-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aa66ae5c-2bd2-4444-8178-b55651e054ef","quote":"ORSERDU is indicated for the treatment of postmenopausal women or adult men with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)‑negative, ESR1 -mutated advanced or metastatic breast cancer","status":"current"},{"value":"Hormone receptor-positive (guideline >= 1% nuclei)","drugId":"alpelisib","cancerId":"breast-hr-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b20b4e18-7a4b-4500-a08f-06c6dab0ee5b","quote":"PIQRAY is indicated in combination with fulvestrant for the treatment of adults with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated, advanced or metastatic breast cancer","status":"current"},{"value":"Hormone receptor-positive (guideline >= 1% nuclei)","drugId":"capivasertib","cancerId":"breast-hr-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d698c106-2322-401e-b738-cbd83c843ecf","quote":"in combination with fulvestrant for the treatment of adult patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, locally advanced or metastatic breast cancer with one or more PIK3CA/AKT1/PTEN -alterations","status":"current"}],"definedBy":{"label":"ASCO/CAP estrogen and progesterone receptor testing guideline, 2020 update (Allison et al., J Clin Oncol)","url":"https://doi.org/10.1200/JCO.19.02309"},"tests":["oncotype-dx-breast"],"assays":[],"companionDiagnostics":[],"forPatient":"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."},"route":"/biomarkers/er-status/","neighbours":{"biomarker":[{"id":"esr1-mutation-ctdna","kind":"biomarker","name":"ESR1 mutation (ligand-binding domain, usually in ctDNA)","route":"/biomarkers/esr1-mutation-ctdna/"},{"id":"ki-67-index","kind":"biomarker","name":"Ki-67 index (proliferation by IHC)","route":"/biomarkers/ki-67-index/"},{"id":"pr-status","kind":"biomarker","name":"PR status (progesterone receptor by IHC)","route":"/biomarkers/pr-status/"}],"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"endometrial","kind":"cancer","name":"Endometrial cancer","route":"/cancers/endometrial/"},{"id":"hr-positive-early-high-risk","kind":"cancer","name":"High-risk early HR-positive breast cancer","route":"/cancers/hr-positive-early-high-risk/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"hr-positive-metastatic-post-cdk46","kind":"cancer","name":"HR-positive metastatic breast cancer after CDK4/6 inhibitors","route":"/cancers/hr-positive-metastatic-post-cdk46/"}],"drug":[{"id":"abemaciclib","kind":"drug","name":"Abemaciclib","route":"/drugs/abemaciclib/"},{"id":"alpelisib","kind":"drug","name":"Alpelisib","route":"/drugs/alpelisib/"},{"id":"capivasertib","kind":"drug","name":"Capivasertib","route":"/drugs/capivasertib/"},{"id":"elacestrant","kind":"drug","name":"Elacestrant","route":"/drugs/elacestrant/"},{"id":"fulvestrant","kind":"drug","name":"Fulvestrant","route":"/drugs/fulvestrant/"},{"id":"letrozole","kind":"drug","name":"Letrozole (and other aromatase inhibitors)","route":"/drugs/letrozole/"},{"id":"palbociclib","kind":"drug","name":"Palbociclib","route":"/drugs/palbociclib/"},{"id":"ribociclib","kind":"drug","name":"Ribociclib","route":"/drugs/ribociclib/"},{"id":"tamoxifen","kind":"drug","name":"Tamoxifen","route":"/drugs/tamoxifen/"}],"term":[{"id":"hormone-receptor-status","kind":"term","name":"Hormone receptor status (ER / PR)","route":"/terms/hormone-receptor-status/"},{"id":"ihc","kind":"term","name":"Immunohistochemistry (IHC)","route":"/terms/ihc/"},{"id":"serd","kind":"term","name":"Selective oestrogen receptor degrader (SERD)","route":"/terms/serd/"}],"target":[{"id":"estrogen-receptor","kind":"target","name":"Estrogen receptor (ERα)","route":"/targets/estrogen-receptor/"}]}}