Hayes DF (2019) HER2 and breast cancer—A phenomenal success story. N Engl J Med 381:1284–1286. https://doi.org/10.1056/NEJMCIBR1909386

Article  PubMed  Google Scholar 

Wolff AC, Hammond MEH, Schwartz JN et al (2007) American Society of clinical oncology/College of American pathologists guideline recommendations for human epidermal growth factor receptor 2 testing in breast cancer. J Clin Oncol 25:118–145. https://doi.org/10.1200/JCO.2006.09.2775

Article  CAS  PubMed  Google Scholar 

Tozbikian GH, Zynger DL (2018) HER2 equivocal breast cancer that is positive by alternative probe HER2 FISH are classified as HER2 negative by oncotype DX. Breast J 24:535–540. https://doi.org/10.1111/TBJ.13004

Article  CAS  PubMed  Google Scholar 

Schlam I, Church SE, Hether TD et al (2021) The tumor immune microenvironment of primary and metastatic HER2- positive breast cancers utilizing gene expression and spatial proteomic profiling. J Transl Med 19:480. https://doi.org/10.1186/s12967-021-03113-9

Article  CAS  PubMed  PubMed Central  Google Scholar 

Zhang H, Katerji H, Turner BM et al (2022) HER2-low breast cancersnew opportunities and challenges. Am J Clin Pathol 157:328–336. https://doi.org/10.1093/AJCP/AQAB117

Article  CAS  PubMed  Google Scholar 

Poh A (2022) T-DXd: new standard for HER2-low breast cancer. Cancer Discov 12:1828. https://doi.org/10.1158/2159-8290.CD-NB2022-0043

Article  Google Scholar 

Modi S, Jacot W, Yamashita T et al (2022) Trastuzumab deruxtecan in previously treated HER2-low advanced breast cancer. N Engl J Med. https://doi.org/10.1056/NEJMOA2203690/SUPPL_FILE/NEJMOA2203690_DATA-SHARING.PDF

Article  PubMed  PubMed Central  Google Scholar 

Geukens T, De Schepper M, Richard F et al (2023) Intra-patient and inter-metastasis heterogeneity of HER2-low status in metastatic breast cancer. Eur J Cancer 188:152–160. https://doi.org/10.1016/j.ejca.2023.04.026

Article  CAS  PubMed  Google Scholar 

van’t Veer LJ, Paik S, Hayes DF (2005) Gene expression profiling of breast cancer: a new tumor marker. J Clin Oncol 23:1631–1635. https://doi.org/10.1200/JCO.2005.12.005

Article  CAS  Google Scholar 

Paik S, Shak S, Tang G et al (2004) A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. N Engl J Med 351:2817–2826. https://doi.org/10.1056/NEJMOA041588

Article  CAS  PubMed  Google Scholar 

Jacobs F, Gaudio M, Benvenuti C et al (2022) Controversies and opportunities in the clinical daily use of the 21-gene assay for prognostication and prediction of chemotherapy benefit in HR+/HER2- early breast cancer. Cancers (Basel). https://doi.org/10.3390/cancers15010148

Article  PubMed  Google Scholar 

Sparano JA, Gray RJ, Makower DF et al (2018) Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. N Engl J Med 379:111–121. https://doi.org/10.1056/NEJMOA1804710

Article  CAS  PubMed  PubMed Central  Google Scholar 

Kalinsky K, Barlow WE, Gralow JR et al (2021) 21-gene assay to inform chemotherapy benefit in node-positive breast cancer. N Engl J Med 385:2336–2347. https://doi.org/10.1056/NEJMoa2108873

Article  CAS  PubMed  PubMed Central  Google Scholar 

Syed YY, Oncotype DX (2020) Breast recurrence score®: a review of its use in early-stage breast cancer. Mol Diagn Ther 24:621–632. https://doi.org/10.1007/S40291-020-00482-7

Article  PubMed  Google Scholar 

Mutai R, Barkan T, Moore A et al (2021) Prognostic impact of HER2-low expression in hormone receptor positive early breast cancer. Breast 60:62–69. https://doi.org/10.1016/j.breast.2021.08.016

Article  PubMed  PubMed Central  Google Scholar 

Wolff AC, Hammond MEH, Allison KH et al (2018) Human epidermal growth factor receptor 2 testing in breast cancer: American society of clinical oncology/College of American pathologists clinical practice guideline focused update. J Clin Oncol 36:2105–2122. https://doi.org/10.1200/JCO.2018.77.8738

Article  CAS  PubMed  Google Scholar 

Munoz-Arcos LS, Nicolo’ E, Newman LA et al (2023) Impact of HER2 low expression in the oncotype DX RS in patients with operable hormone receptor positive early stage breast cancer. J Clin Oncol 41:575. https://doi.org/10.1200/JCO.2023.41.16_suppl.575

Article  Google Scholar 

Noske A, Loibl S, Darb-Esfahani S et al (2011) Comparison of different approaches for assessment of HER2 expression on protein and mRNA level: prediction of chemotherapy response in the neoadjuvant GeparTrio trial (NCT00544765). Breast Cancer Res Treat 126:109–117. https://doi.org/10.1007/s10549-010-1316-y

Article  CAS  PubMed  Google Scholar 

Furrer D, Paquet C, Jacob S et al (2018) The Human epidermal growth factor receptor 2 (HER2) as a prognostic and predictive biomarker: molecular insights into HER2 activation and diagnostic implications. In: Lemamy GJ (ed) Cancer prognosis. IntechOpen, London. https://doi.org/10.5772/intechopen.78271

Chapter  Google Scholar 

Gheni N, Westenberg D (2020) Quantitative real-time PCR assay with immunohistochemical evaluation of HER2/neu oncogene in breast cancer patients and its correlation with clinicopathological findings. Indian J Pathol Microbiol 63:123–128. https://doi.org/10.4103/IJPM.IJPM_136_19

Article  Google Scholar 

Zoppoli G, Garuti A, Cirmena G et al (2017) Her2 assessment using quantitative reverse transcriptase polymerase chain reaction reliably identifies Her2 overexpression without amplification in breast cancer cases. J Transl Med 15:91. https://doi.org/10.1186/s12967-017-1195-7

Article  CAS  PubMed  PubMed Central  Google Scholar 

Tvrdík D, Staněk L, Skálová H et al (2012) Comparison of the IHC, FISH, SISH and qPCR methods for the molecular diagnosis of breast cancer. Mol Med Rep 6:439–443. https://doi.org/10.3892/mmr.2012.919

Article  CAS  PubMed  Google Scholar 

Koudelakova V, Berkovcova J, Trojanec R et al (2015) Evaluation of HER2 gene status in breast cancer samples with indeterminate fluorescence in situ hybridization by quantitative real-time PCR. J Mol Diagn 17:446–455. https://doi.org/10.1016/j.jmoldx.2015.03.007

Article  CAS  PubMed  Google Scholar 

Cronin M, Pho M, Dutta D et al (2004) Measurement of gene expression in archival paraffin-embedded tissues: development and performance of a 92-gene reverse transcriptase-polymerase chain reaction assay. Am J Pathol 164:35–42. https://doi.org/10.1016/S0002-9440(10)63093-3

Article  CAS  PubMed  PubMed Central  Google Scholar 

Esteva FJ, Sahin AA, Cristofanilli M et al (2005) Prognostic role of a multigene reverse transcriptase-PCR assay in patients with node-negative breast cancer not receiving adjuvant systemic therapy. Clin Cancer Res Off J Am Assoc Cancer Res 11:3315–3319. https://doi.org/10.1158/1078-0432.CCR-04-1707

Article  CAS  Google Scholar 

Chang JC, Makris A, Gutierrez MC et al (2005) Predicting response to primary chemotherapy: gene expression profiling of paraffin-embedded core biopsy tissue. Clin Cancer Res Off J Am Assoc Cancer Res 11:3315–3319. https://doi.org/10.1007/s10549-006-9366-x

Article  CAS  Google Scholar 

Cobleigh MA, Tabesh B, Bitterman P et al (2005) Tumor gene expression and prognosis in breast cancer patients with 10 or more positive lymph nodes. Clin Cancer Res 11:8623–8631. https://doi.org/10.1158/1078-0432.CCR-05-0735

Article  CAS  PubMed  Google Scholar 

Baehner FL, Achacoso N, Maddala T et al (2010) Human epidermal growth factor receptor 2 assessment in a case-control study: comparison of fluorescence in situ hybridization and quantitative reverse transcription polymerase chain reaction performed by central laboratories. J Clin Oncol 28:4300–4306. https://doi.org/10.1200/JCO.2009.24.8211

Article  PubMed  Google Scholar 

Zattarin E, Presti D, Mariani L et al (2023) Prognostic significance of HER2-low status in HR-positive/HER2-negative advanced breast cancer treated with CDK4/6 inhibitors. npj Breast Cancer 9:27. https://doi.org/10.1038/s41523-023-00534-1

Article  CAS  PubMed  PubMed Central  Google Scholar 

Tarantino P, Jin Q, Tayob N et al (2022) Prognostic and biologic significance of ERBB2-low expression in early-stage breast cancer. JAMA Oncol 8:1177–1183. https://doi.org/10.1001/JAMAONCOL.2022.2286

Article  PubMed  PubMed Central  Google Scholar 

Molinelli C, Jacobs F, Agostinetto E et al (2023) Prognostic value of HER2-low status in breast cancer: a systematic review and meta-analysis. ESMO open 8:101592. https://doi.org/10.1016/j.esmoop.2023.101592

Article  CAS  PubMed  PubMed Central  Google Scholar 

Dvorak L, Dolan M, Fink J et al (2013) Correlation between HER2 determined by fluorescence in situ hybridization and reverse transcription-polymerase chain reaction of the oncotype DX test. Appl Immunohistochem Mol Morphol AIMM 21:196–199. https://doi.org/10.1097/PAI.0B013E3182632FF5

Article  CAS  PubMed  Google Scholar 

Metzger Filho O, Viale G, Trippa L et al (2019) HER2 heterogeneity as a predictor of response to neoadjuvant T-DM1 plus pertuzumab: results from a prospective clinical trial. J Clin Oncol 37:502. https://doi.org/10.1200/JCO.2019.37.15_suppl.502

Article  Google Scholar 

Schettini F, Chic N, Brasó-Maristany F et al (2021) Clinical, pathological, and PAM50 gene expression features of HER2-low breast cancer. npj Breast Cancer 7:1. https://doi.org/10.1038/s41523-020-00208-2

Article