最近，人表皮生长因子 2 (HER2) 低（即 HER2 评分为 1 或 2，无扩增）乳腺癌患者有资格接受曲妥珠单抗-deruxtecan 治疗。为了提高 HER2-low 检测的标准化和定量检测，我们在荷兰进行了一项类似外部质量评估的研究。动态范围细胞系和免疫组织化学 (IHC) 校准品用于量化 HER2 表达并评估实验室间变异性。35 个实验室使用常规 HER2 检测对三张带有动态范围细胞系和 IHC 校准品的空白载玻片进行染色。使用四种不同的抗体克隆：19 个 (54.3%) 4B5、6 个 (17.1%) A0485、5 个 (14.3%) DG44 (HercepTest) 和 5 个 (14.3%) SP3。实验室使用两种不同的检测试剂盒进行 4B5 检测：14 个 (73.7%) ultraView 和 5 个 (26.3%) OptiView。使用人工智能软件测量的细胞系中 HER2 表达的变异性为中位数（最小-最大） = 阴性核心 0.5%（0.0-57.0）、1 核心 4.3%（1.6-71.3）、2 核心 42.8%（30.4-92.6） ）和 3 核 96.2% (91.8-98.8)。校准器 DG44 和 4B5 OptiView 具有最高的分析灵敏度，紧随其后的是 4B5 ultraView。 SP3 是最不敏感的。由于背景染色，A0485 检测的校准品无法分析。由于检测已验证可检测 HER2 扩增的肿瘤，但并非所有检测和抗体都适合 HER2 低检测。一些测试显示阴性细胞系中有明显的表达。使用校准器的动态范围细胞系对照和定量分析表明，实验室间的变异性比通常认为的要大。需要实验室对 HER2 检测进行重新验证，以确保 HER2 低检测适用于临床。© 2024 作者。组织病理学由约翰·威利出版

Recently, human epidermal growth factor 2 (HER2)-low (i.e. HER2 score 1+ or 2+ without amplification) breast cancer patients became eligible for trastuzumab-deruxtecan treatment. To improve assay standardisation and detection of HER2-low in a quantitative manner, we conducted an external quality assessment-like study in the Netherlands. Dynamic range cell lines and immunohistochemistry (IHC) calibrators were used to quantify HER2 expression and to assess interlaboratory variability.Three blank slides with a dynamic range cell line and an IHC calibrator were stained with routine HER2 assays by 35 laboratories. Four different antibody clones were used: 19 (54.3%) 4B5, six (17.1%) A0485, five (14.3%) DG44 (HercepTest) and five (14.3%) SP3. Laboratories used two different detection kits for 4B5 assays: 14 (73.7%) ultraView and five (26.3%) OptiView. Variability of HER2 expression in cell lines, measured with artificial intelligence software, was median (min-max) = negative core 0.5% (0.0-57.0), 1+ core 4.3% (1.6-71.3), 2+ core 42.8% (30.4-92.6) and 3+ core 96.2% (91.8-98.8). The calibrators DG44 and 4B5 OptiView had the highest analytical sensitivity, closely followed by 4B5 ultraView. SP3 was the least sensitive. Calibrators of A0485 assays were not analysable due to background staining.As assays were validated for detecting HER2-amplified tumours, not all assays and antibodies proved suitable for HER2-low detection. Some tests showed distinct expression in the negative cell line. Dynamic range cell line controls and quantitative analysis using calibrators demonstrated more interlaboratory variability than commonly appreciated. Revalidation of HER2 tests by laboratories is needed to ensure clinical applicable HER2-low assays.© 2024 The Author(s). Histopathology published by John Wiley & Sons Ltd.