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Purpose: The proven efficacy of human epidermal growth factor receptor 2 (HER2) antibody-drug conjugate therapy for treating HER2-low breast cancers necessitates more accurate and reproducible HER2 immunohistochemistry (IHC) scoring. We aimed to validate performance and utility of a fully automated artificial intelligence (AI) solution for interpreting HER2 IHC in breast carcinoma.
Materials And Methods: A two-arm multireader study of 120 HER2 IHC whole-slide images from four sites assessed HER2 scoring by four surgical pathologists without and with the aid of an AI HER2 solution. Both arms were compared with high-confidence ground truth (GT) established by agreement of at least four of five breast pathology subspecialists according to ASCO/College of American Pathologists (CAP) 2018/2023 guidelines.
Results: The mean interobserver agreement among GT pathologists across all HER2 scores was 72.4% (N = 120). The AI solution demonstrated high accuracy for HER2 scoring, with 92.1% agreement on slides with high confidence GT (n = 92). The use of the AI tool led to improved performance by readers, interobserver agreement increased from 75.0% for digital manual read to 83.7% for AI-assisted review, and scoring accuracy improved from 85.3% to 88.0%. For the distinction of HER2 0 from 1+ cases (n = 58), pathologists supported by AI showed significantly higher interobserver agreement (69.8% without AI 87.4% with AI) and accuracy (81.9% without AI 88.8% with AI).
Conclusion: This study demonstrated utility of a fully automated AI solution to aid in scoring HER2 IHC accurately according to ASCO/CAP 2018/2023 guidelines. Pathologists supported by AI showed improvements in HER2 IHC scoring consistency and accuracy, especially for distinguishing HER2 0 from 1+ cases. This AI solution could be used by pathologists as a decision support tool for enhancing reproducibility and consistency of HER2 scoring and particularly for identifying HER2-low breast cancers.
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http://dx.doi.org/10.1200/PO.24.00353 | DOI Listing |
ESMO Open
September 2025
Department of Medical Oncology, Hospital Clínic Barcelona, Barcelona, Spain; Translational Genomics and Targeted Therapies in Solid Tumors, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain; Faculty of Medicine, University of Barcelona, Barcelona, Spain; Clínic Barcelona
Background: Response to trastuzumab combined with chemotherapy (T-chemo) in human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer (AGC) varies widely, highlighting the need for more precise biomarkers beyond conventional HER2 assessment with immunohistochemistry (IHC) and in situ hybridization (ISH). The HER2DX ERBB2 messenger RNA (mRNA) assay, a clinically validated genomic test initially developed for early-stage HER2-positive breast cancer, quantitatively measures ERBB2 expression and may improve patient selection for T-chemo in AGC.
Patients And Methods: In a retrospective cohort of 134 patients with AGC, including 58 who received T-chemo, we evaluated whether the HER2DX ERBB2 score defines more accurately HER2 status and correlates with treatment response and survival outcomes in HER2-positive AGC, compared with standard pathology-based methods.
Small Methods
September 2025
Department of Pathology, College of Medicine, Hanyang University, Seoul, Republic of Korea.
While human epidermal growth factor receptor (HER2) has emerged as a tumor-agnostic biomarker, standard HER2 testing for anti-HER2 therapies using immunohistochemistry (IHC) and in situ hybridization (ISH) assays remains subjective, time-consuming, and often inaccurate. To address these limitations, an ultrafast and precise HER2 testing method is developed using Lab-On-An-Array (LOAA) digital real-time PCR (drPCR), a fully automated digital PCR enabling real-time absolute quantification. A multicenter study involving four independent breast cancer cohorts cross-validates the high diagnostic accuracy of drPCR-based HER2 assessment.
View Article and Find Full Text PDFBreast cancer is a heterogeneous disease with numerous histological subtypes. Invasive lobular cancer (ILC) is the most common special subtype, accounting for 10-15% of all breast cancers. The pathognomonic feature of ILC is the loss of E-cadherin (CDH1), which leads to a unique single-file growth pattern of discohesive cells.
View Article and Find Full Text PDFQuant Imaging Med Surg
September 2025
Department of Radiology, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, University of Electronic Science and Technology of China, Chengdu, China.
Background: Accurate preoperative human epidermal growth factor receptor 2 (HER2) status assessment is crucial for guiding treatment selection, particularly with the emergence of anti-HER2 antibody-drug conjugates (ADCs) for HER2-low breast cancer. However, current immunohistochemistry (IHC)-based classification is limited by spatial heterogeneity and sampling bias. Quantitative analysis of intra- and peri-tumoral heterogeneity (ITH) on imaging may offer a non-invasive, objective, and reproducible approach to distinguish HER2-low breast cancer from other subtypes.
View Article and Find Full Text PDFExpert Opin Biol Ther
September 2025
Division of Medical Oncology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
Introduction: Zanidatamab is a humanized biparatopic IgG antibody that selectively inhibits HER2 signaling pathway by targeting two distinct epitopes in the extracellular domains II and IV of HER2. Zanidatamab received accelerated approval from the United States Food and Drug Administration for the treatment of HER2-positive (immunohistochemistry [IHC] 3+) biliary tract cancer (BTC) in November 2024. Additionally, zanidatamab received approval for the treatment of HER2 IHC 3+ BTC from the European Medicines Agency in June 2025, and from National Medical Products Administration of China in May 2025.
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