针对最近的临床试验显示，抗体药物偶联物治疗在表皮生长因子受体 2 (HER2) 免疫组织化学得分为 1+ 或 2+、原位杂交阴性的乳腺癌 (BC) 中具有临床益处的情况下，产生了“HER2 低度 BC” 的新概念，以描述这种新的相关治疗类别的 BC。HER2 低度 BC 的临床认识导致了治疗领域和 BC 患者管理的范式转变，并导致临床实践指南的迅速变化。此外，美国临床肿瘤学会-美国病理学家学会 (ASCO-CAP) 最近更新了其 HER2 指南建议，专门针对 HER2 低度 BC 进行了说明。我们在 PubMed 上进行了同行评审文章、监管沟通以及与 HER2 低度 BC 相关的相关实践指南的文献搜索。在本综述中，我们总结了当前已发表的有关 HER2 低度 BC 的临床病理学和分子特征、诊断标准以及最新的指南建议，并强调了在日常临床实践中鉴定 HER2 低度 BC 时仍面临的实际和诊断挑战。版权所有 © 2023 Wolters Kluwer Health, Inc. 保留所有权利。

In response to recent clinical trials that demonstrate the clinical benefit of antibody-drug conjugate drug therapy in breast cancer (BC) with human epidermal growth factor 2 (HER2) immunohistochemical scores of 1+ or 2+ and negative in situ hybridization results, a new concept of "HER2-low BC" has emerged to describe this newly relevant therapeutic category of BC. Clinical recognition of HER2-low BC has caused a paradigm shift in the therapeutic landscape and management of patients with BC and resulted in rapid changes in clinical practice guidelines. In addition the American Society of Clinical Oncology-College of American Pathologists (ASCO-CAP) recently updated their HER2 Guidelines Recommendations to specifically address HER2-low BC. A literature search in PubMed of peer-reviewed articles, regulatory communications, and relevant practice guidelines pertaining to HER2-low BC was conducted. In this review, we have summarized current published knowledge regarding the clinicopathologic and molecular features, diagnostic criteria, and most current guideline recommendations regarding HER2-low BC, and also highlight ongoing practical and diagnostic challenges when identifying HER2-low BC in routine clinical practice.Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.