在许多国家，常规对导管原位癌（DCIS）进行激素受体状态评估，因为激素受体阳性的DCIS患者有资格接受辅助抗激素治疗，旨在降低同侧和对侧乳腺癌风险。尽管 HER2 基因扩增及其相关的 HER2 蛋白过度表达构成了浸润性乳腺癌的主要预后和预测标志物，但其在 DCIS 的诊断和治疗中的应用并不那么简单。 HER2 免疫组织化学尚未常规进行，因为 HER2 阳性在 DCIS 生物学中的作用尚不清楚。尽管如此，最近的数据对这种做法提出了挑战。在这里，我们讨论常规 HER2 评估对 DCIS 的价值。 HER2 阳性与 DCIS 分级密切相关：大约五分之四的 HER2 阳性 DCIS 表现出高度异型性。由于形态学 DCIS 分级容易出现观察者间的变异，HER2 免疫组织化学可以使分级更加稳健。多项研究表明 HER2 阳性 DCIS 与同侧复发风险之间存在关联，尽管目前尚不清楚这是整体复发、原位复发还是侵入性复发。 HER2 阳性 DCIS 往往较大，手术切缘受累的风险较高。 HER2 阳性 DCIS 患者从辅助放疗中获益更多：它大大降低了肿瘤切除术后的局部复发风险，且不影响总生存期。单纯活检诊断的 DCIS 中 HER2 阳性与手术后升级为浸润性癌的增加有关。因此，术前活检的 HER2 免疫组织化学可能为外科医生提供有用的信息，有利于更广泛的切除。现在似乎是考虑 DCIS 亚型依赖性治疗的正确时机，包括对 HER2 阳性 DCIS 患者进行适当的局部治疗，以及对激素受体阳性、HER2 阴性 DCIS 患者进行降级治疗。© 2024。作者。

In many countries, hormone receptor status assessment of ductal carcinoma in situ (DCIS) is routinely performed, as hormone receptor-positive DCIS patients are eligible for adjuvant anti-hormonal treatment, aiming to reduce the ipsilateral and contralateral breast cancer risk. Although HER2 gene amplification and its associated HER2 protein overexpression constitute a major prognostic and predictive marker in invasive breast carcinoma, its use in the diagnosis and treatment of DCIS is less straightforward. HER2 immunohistochemistry is not routinely performed yet, as the role of HER2-positivity in DCIS biology is unclear. Nonetheless, recent data challenge this practice. Here, we discuss the value of routine HER2 assessment for DCIS. HER2-positivity correlates strongly with DCIS grade: around four in five HER2-positive DCIS show high grade atypia. As morphological DCIS grading is prone to interobserver variability, HER2 immunohistochemistry could render grading more robust. Several studies showed an association between HER2-positive DCIS and ipsilateral recurrence risk, albeit currently unclear whether this is for overall, in situ or invasive recurrence. HER2-positive DCIS tends to be larger, with a higher risk of involved surgical margins. HER2-positive DCIS patients benefit more from adjuvant radiotherapy: it substantially decreases the local recurrence risk after lumpectomy, without impact on overall survival. HER2-positivity in pure biopsy-diagnosed DCIS is associated with increased upstaging to invasive carcinoma after surgery. HER2 immunohistochemistry on preoperative biopsies might therefore provide useful information to surgeons, favoring wider excisions. The time seems right to consider DCIS subtype-dependent treatment, comprising appropriate local treatment for HER2-positive DCIS patients and de-escalation for hormone receptor-positive, HER2-negative DCIS patients.© 2024. The Author(s).