Abstract：
OBJECTIVE: Human epidermal growth factor receptor 2 (HER2) expression is an important biomarker in breast cancer (BC). Most BC cases categorised as HER2-negative (HER2-) express low levels of HER2 [immunohistochemistry (IHC) 1+ or IHC 2+/in-situ hybridisation not amplified (ISH-)] and represent a clinically relevant therapeutic category that is amenable to targeted therapy using a recently approved HER2-directed antibody-drug conjugate. A group of practising pathologists, with expertise in breast pathology and BC biomarker testing, outline best practices and guidance for achieving consensus in HER2 IHC scoring for BC.
RESULTS: The authors describe current knowledge and challenges of IHC testing and scoring of HER2-low expressing BC and provide best practices and guidance for accurate identification of BCs expressing low levels of HER2. These expert pathologists propose an algorithm for assessing HER2 expression with validated IHC assays and incorporate the 2023 American Society of Clinical Oncology and College of American Pathologist guideline update. The authors also provide guidance on when to seek consensus for HER2 IHC scoring, how to incorporate HER2-low into IHC reporting and present examples of HER2 IHC staining, including challenging cases.
CONCLUSIONS: Awareness of BC cases that are negative for HER protein overexpression/gene amplification and the related clinical relevance for targeted therapy highlight the importance of accurate HER2 IHC scoring for optimal treatment selection.
RESULTS: The authors describe current knowledge and challenges of IHC testing and scoring of HER2-low expressing BC and provide best practices and guidance for accurate identification of BCs expressing low levels of HER2. These expert pathologists propose an algorithm for assessing HER2 expression with validated IHC assays and incorporate the 2023 American Society of Clinical Oncology and College of American Pathologist guideline update. The authors also provide guidance on when to seek consensus for HER2 IHC scoring, how to incorporate HER2-low into IHC reporting and present examples of HER2 IHC staining, including challenging cases.
CONCLUSIONS: Awareness of BC cases that are negative for HER protein overexpression/gene amplification and the related clinical relevance for targeted therapy highlight the importance of accurate HER2 IHC scoring for optimal treatment selection.
摘要：
目的：人表皮生长因子受体2（HER2）的表达是乳腺癌（BC）的重要生物标志物。分类为HER2阴性（HER2-）的大多数BC病例表达低水平的HER2[免疫组织化学（IHC）1或IHC2/原位杂交未扩增（ISH-）]，并且代表了临床相关的治疗类别，适合使用最近批准的针对HER2的抗体-药物偶联物进行靶向治疗。一群执业病理学家，具有乳腺病理学和BC生物标志物检测方面的专业知识，概述在BC的HER2IHC评分中达成共识的最佳实践和指南.
结果：作者描述了目前关于HER2低表达BC的IHC检测和评分的知识和挑战，并为准确鉴定表达低水平HER2的BC提供了最佳实践和指导。这些专家病理学家提出了一种通过验证的IHC测定评估HER2表达的算法，并纳入了2023年美国临床肿瘤学会和美国病理学家指南更新。作者还提供了关于何时寻求HER2IHC评分共识的指导，如何将低HER2纳入IHC报告并介绍HER2IHC染色的例子，包括具有挑战性的案件。
结论：对HER蛋白过表达/基因扩增阴性的BC病例的认识以及与靶向治疗相关的临床相关性突出了准确的HER2IHC评分对于最佳治疗选择的重要性。
结果：作者描述了目前关于HER2低表达BC的IHC检测和评分的知识和挑战，并为准确鉴定表达低水平HER2的BC提供了最佳实践和指导。这些专家病理学家提出了一种通过验证的IHC测定评估HER2表达的算法，并纳入了2023年美国临床肿瘤学会和美国病理学家指南更新。作者还提供了关于何时寻求HER2IHC评分共识的指导，如何将低HER2纳入IHC报告并介绍HER2IHC染色的例子，包括具有挑战性的案件。
结论：对HER蛋白过表达/基因扩增阴性的BC病例的认识以及与靶向治疗相关的临床相关性突出了准确的HER2IHC评分对于最佳治疗选择的重要性。
