{"entity":{"id":"her2-ish-amplified","kind":"biomarker","name":"HER2 ISH amplified (ERBB2 gene amplification)","aka":["HER2 ISH+","HER2 FISH positive","ERBB2 amplification","HER2 amplified","HER2/CEP17 ratio >= 2.0","HER2 gene amplification","HER2 Dual ISH"],"tldr":"ISH counts copies of the HER2 gene in each tumour cell. A ratio of 2 or more against the chromosome 17 control, or 6 or more copies per cell, is amplified and HER2-positive whatever the protein stain showed.","summary":"In situ hybridisation (fluorescent FISH or chromogenic dual ISH) measures ERBB2 gene copies. Under ASCO/CAP 2018, a HER2/CEP17 ratio >= 2.0 with an average HER2 copy number >= 4.0 per cell is positive (group 1); a ratio < 2.0 with copy number >= 6.0 is positive (group 3); ratio >= 2.0 with copy number < 4.0 (group 2) and ratio < 2.0 with copy number 4.0 to < 6.0 (group 4) need concurrent IHC and are positive only if the IHC is 3+ (or 2+ on recount for group 4 in some readings). Labels for trastuzumab, pertuzumab, trastuzumab emtansine and trastuzumab deruxtecan accept ISH+ as HER2-positive; the FDA list carries the HER2 FISH pharmDx, PathVysion, INFORM HER-2/neu, SPOT-LIGHT CISH and Ventana Dual ISH kits as companion diagnostics.","asOf":"2026-09-23","links":[{"label":"ASCO/CAP HER2 testing in breast cancer guideline, 2018 focused update (Wolff et al., J Clin Oncol)","url":"https://doi.org/10.1200/JCO.2018.77.8738"},{"label":"FDA: List of FDA-Authorized Companion Diagnostic Devices","url":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"}],"tags":["biomarker","her2"],"related":["her2-ihc-3-plus","her2-ihc-2-plus"],"cancers":["breast-her2-positive","gastric-her2-positive","her2-positive-early-breast-cancer","colorectal","gallbladder","biliary-tract-cancer"],"sections":[],"technologies":[],"targets":[],"drugs":["trastuzumab","pertuzumab","trastuzumab-emtansine","trastuzumab-deruxtecan","her2-testing-assays"],"companies":[],"institutions":[],"pathways":[],"terms":["fish","gene-amplification","her2-positive","her2-testing-in-biliary-cancer"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":["paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015","paper-sartore-bianchi-heracles-trastuzumab-lapatinib-lancet-oncol-2016","paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016","paper-nakamura-triumph-ctdna-pertuzumab-trastuzumab-her2-colorectal-nat-med-2021","paper-harding-lancet-oncol","paper-angerilli-her2-ihc-cish-biliary-hum-pathol-2026","paper-mondaca-erbb2-gallbladder-us-chile-jco-go-2024"],"journals":[],"dependsOn":[],"notes":["Colorectal cancer: the HERACLES diagnostic criteria, not the breast or gastric ones, define positivity. A tumour is HER2-positive when intense membranous HER2 staining is present in more than 50% of cells (immunohistochemistry 3+), or immunohistochemistry 2+ with in situ hybridisation confirmation in more than 50% of cells; in the validation, no immunohistochemistry 0 or 1+ case was amplified and silver and fluorescence in situ hybridisation agreed completely (Valtorta 2015). That threshold selects about 5% of RAS wild-type patients (48 of 914 screened for HERACLES) and 2 to 3% of all colorectal cancers. Plasma HER2 copy number, adjusted for tumour fraction, selected patients as well as tissue in TRIUMPH (Nakamura 2021).","Gallbladder and biliary cancer: ERBB2 amplification confirmed by central ISH was the entry criterion of HERIZON-BTC-01 (Harding 2023). By sequencing, amplification was present in 8% of 260 gallbladder cancer patients alone and 1.5% with a mutation (Mondaca 2024) and in 10.2% of 244 samples in cBioPortal gbc_mskcc_2022. Chromogenic dual ISH found amplification in all IHC 3+ and some 2+ and 1+ tumours (Angerilli 2026)."],"target":"her2","measurement":"fish-ratio","scoringRule":{"text":"HER2/CEP17 ratio >= 2.0 with mean HER2 copy number >= 4.0 signals per cell is amplified; ratio < 2.0 with copy number >= 6.0 is also amplified; other combinations are resolved with concurrent immunohistochemistry.","quote":"HER-2/neu (ERBB2) gene amplification (ISH amplified)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools","sourceLabel":"FDA: List of FDA-Authorized Companion Diagnostic Devices"},"thresholds":[{"value":"ISH+ (IHC 3+ or ISH+)","drugId":"trastuzumab-deruxtecan","cancerId":"breast-her2-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=7e67e73e-ddf4-4e4d-8b50-09d7514910b6","quote":"based on confirmed HER2-positive status or HER2 gene amplification (IHC 3+ or ISH+)","status":"current"},{"value":"HER2 gene amplification","drugId":"trastuzumab","cancerId":"breast-her2-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=492dbdb2-077e-4064-bff3-372d6af0a7a2","quote":"Select patients based on HER2 protein overexpression or HER2 gene amplification in tumor specimens","status":"current"},{"value":"HER2 gene amplification","drugId":"pertuzumab","cancerId":"breast-her2-positive","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=17f85d17-ab71-4f5b-9fe3-0b8c822f69ff","quote":"Assessment of HER2 protein overexpression and HER2 gene amplification should be performed using FDA-approved tests specific for breast cancer by laboratories with demonstrated proficiency.","status":"current"}],"tests":[],"assays":["her2-ish"],"companionDiagnostics":[{"device":"HER2 FISH pharmDx Kit","maker":"Dako Denmark A/S (Agilent)","companyId":"agilent","drugs":["trastuzumab"],"indication":"Breast Cancer - Tissue","pma":"P040005 (05/03/2005)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"},{"device":"HER2 FISH pharmDx Kit","maker":"Dako Denmark A/S (Agilent)","companyId":"agilent","drugs":["trastuzumab"],"indication":"Gastric and Gastroesophageal Cancer - Tissue","pma":"P040005/S005 (10/20/2010)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"},{"device":"PathVysion HER-2 DNA Probe Kit","maker":"Abbott Molecular","companyId":"abbott","drugs":["trastuzumab"],"indication":"Breast Cancer - Tissue","pma":"P980024 (12/11/1998)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"},{"device":"Ventana HER2 Dual ISH DNA Probe Cocktail","maker":"Ventana Medical Systems (Roche)","drugs":["trastuzumab"],"indication":"Breast Cancer - Tissue","pma":"P190031 (07/28/2020)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"},{"device":"Ventana HER2 Dual ISH DNA Probe Cocktail","maker":"Ventana Medical Systems (Roche)","drugs":["trastuzumab-deruxtecan","pertuzumab"],"indication":"Breast Cancer - Tissue","pma":"P190031/S014 (12/15/2025)","source":"https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools"}],"forPatient":"An amplified ISH result means your cancer has extra copies of the HER2 gene and is HER2-positive, so trastuzumab-based treatment applies even if the protein stain was only 2+. A non-amplified result after a 2+ stain means HER2-low. The ratio and copy number on the report are what the pathologist used; ask for them if the report only says positive or negative."},"route":"/biomarkers/her2-ish-amplified/","neighbours":{"biomarker":[{"id":"her2-mutation","kind":"biomarker","name":"HER2 (ERBB2) activating mutation","route":"/biomarkers/her2-mutation/"},{"id":"her2-ihc-2-plus","kind":"biomarker","name":"HER2 IHC 2+ (equivocal, reflex to ISH)","route":"/biomarkers/her2-ihc-2-plus/"},{"id":"her2-ihc-3-plus","kind":"biomarker","name":"HER2 IHC 3+ (HER2-positive by immunohistochemistry)","route":"/biomarkers/her2-ihc-3-plus/"}],"cancer":[{"id":"biliary-tract-cancer","kind":"cancer","name":"Biliary tract cancer (all types)","route":"/cancers/biliary-tract-cancer/"},{"id":"colorectal","kind":"cancer","name":"Colorectal cancer","route":"/cancers/colorectal/"},{"id":"her2-positive-early-breast-cancer","kind":"cancer","name":"Early HER2-positive breast cancer","route":"/cancers/her2-positive-early-breast-cancer/"},{"id":"gallbladder","kind":"cancer","name":"Gallbladder cancer","route":"/cancers/gallbladder/"},{"id":"breast-her2-positive","kind":"cancer","name":"HER2-positive breast cancer","route":"/cancers/breast-her2-positive/"},{"id":"gastric-her2-positive","kind":"cancer","name":"HER2-positive gastric cancer","route":"/cancers/gastric-her2-positive/"}],"drug":[{"id":"her2-testing-assays","kind":"drug","name":"HER2 IHC and ISH companion assays (HercepTest, PATHWAY 4B5, HER2 Dual ISH)","route":"/drugs/her2-testing-assays/"},{"id":"pertuzumab","kind":"drug","name":"Pertuzumab","route":"/drugs/pertuzumab/"},{"id":"trastuzumab","kind":"drug","name":"Trastuzumab","route":"/drugs/trastuzumab/"},{"id":"trastuzumab-deruxtecan","kind":"drug","name":"Trastuzumab deruxtecan","route":"/drugs/trastuzumab-deruxtecan/"},{"id":"trastuzumab-emtansine","kind":"drug","name":"Trastuzumab emtansine","route":"/drugs/trastuzumab-emtansine/"}],"term":[{"id":"fish","kind":"term","name":"FISH / ISH (in situ hybridisation)","route":"/terms/fish/"},{"id":"gene-amplification","kind":"term","name":"Gene amplification and copy-number change","route":"/terms/gene-amplification/"},{"id":"her2-testing-in-biliary-cancer","kind":"term","name":"HER2 testing in biliary tract cancer (IHC, ISH and NGS)","route":"/terms/her2-testing-in-biliary-cancer/"},{"id":"her2-positive","kind":"term","name":"HER2-positive (IHC 3+ or ISH-amplified)","route":"/terms/her2-positive/"}],"paper":[{"id":"paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015","kind":"paper","name":"Assessment of a HER2 scoring system for colorectal cancer: results from a validation study","route":"/key-papers/paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015/"},{"id":"paper-nakamura-triumph-ctdna-pertuzumab-trastuzumab-her2-colorectal-nat-med-2021","kind":"paper","name":"Circulating tumor DNA-guided treatment with pertuzumab plus trastuzumab for HER2-amplified metastatic colorectal cancer: a phase 2 trial (TRIUMPH)","route":"/key-papers/paper-nakamura-triumph-ctdna-pertuzumab-trastuzumab-her2-colorectal-nat-med-2021/"},{"id":"paper-mondaca-erbb2-gallbladder-us-chile-jco-go-2024","kind":"paper","name":"Clinical and genomic characterization of ERBB2-altered gallbladder cancer: exploring differences between an American and a Chilean cohort","route":"/key-papers/paper-mondaca-erbb2-gallbladder-us-chile-jco-go-2024/"},{"id":"paper-sartore-bianchi-heracles-trastuzumab-lapatinib-lancet-oncol-2016","kind":"paper","name":"Dual-targeted therapy with trastuzumab and lapatinib in treatment-refractory, KRAS codon 12/13 wild-type, HER2-positive metastatic colorectal cancer (HERACLES)","route":"/key-papers/paper-sartore-bianchi-heracles-trastuzumab-lapatinib-lancet-oncol-2016/"},{"id":"paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016","kind":"paper","name":"HER2 overexpression and amplification as a potential therapeutic target in colorectal cancer: analysis of 3256 patients enrolled in the QUASAR, FOCUS and PICCOLO colorectal cancer trials","route":"/key-papers/paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016/"},{"id":"paper-angerilli-her2-ihc-cish-biliary-hum-pathol-2026","kind":"paper","name":"HER2 status in extrahepatic cholangiocarcinoma and gallbladder carcinoma: concordance between immunohistochemistry and chromogenic in situ hybridization in 140 cases","route":"/key-papers/paper-angerilli-her2-ihc-cish-biliary-hum-pathol-2026/"},{"id":"paper-destiny-crc02-lancet-oncol-2024","kind":"paper","name":"Trastuzumab deruxtecan in patients with HER2-positive advanced colorectal cancer (DESTINY-CRC02): primary results from a multicentre, randomised, phase 2 trial","route":"/key-papers/paper-destiny-crc02-lancet-oncol-2024/"},{"id":"paper-strickler-mountaineer-tucatinib-trastuzumab-lancet-oncol-2023","kind":"paper","name":"Tucatinib plus trastuzumab for chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer (MOUNTAINEER)","route":"/key-papers/paper-strickler-mountaineer-tucatinib-trastuzumab-lancet-oncol-2023/"},{"id":"paper-harding-lancet-oncol","kind":"paper","name":"Zanidatamab for HER2-amplified, unresectable, locally advanced or metastatic biliary tract cancer (HERIZON-BTC-01): a multicentre, single-arm, phase 2b study","route":"/key-papers/paper-harding-lancet-oncol/"}],"target":[{"id":"her2","kind":"target","name":"HER2","route":"/targets/her2/"}]}}