From the Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
Arch Pathol Lab Med. 2021 Jul 1;145(7):883-886. doi: 10.5858/arpa.2020-0273-OA.
CONTEXT.—: Guidelines for HER2 testing in breast cancer have changed over time, from the US Food and Drug Administration guideline to the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines published in 2007, 2013, and 2018.
OBJECTIVE.—: To investigate the change in assignment of HER2 status in breast cancers with equivocal (2+) immunohistochemistry (IHC) results by fluorescence in situ hybridization (FISH) following implementation of the ASCO/CAP 2018 guideline.
DESIGN.—: The study included 3556 invasive breast cancers that were HER2 equivocal (2+) by IHC and were submitted to our FISH laboratory after July 2018. Reflex testing (with repeat IHC staining) was performed on certain categories of FISH results known as groups 2, 3, and 4. Concomitant review of IHC and FISH was performed on these reflex cases per 2018 guideline recommendations. The FISH data were analyzed to compare US Food and Drug Administration and ASCO/CAP 2007, 2013, and 2018 interpretations.
RESULTS.—: Of 3548 invasive breast cancers with complete data available, the percentage agreement for FISH according to different guidelines was highest for ASCO/CAP 2018 versus US Food and Drug Administration (96.5%), followed by ASCO/CAP 2018 versus 2007 (93.8%), and lowest with ASCO/CAP 2018 versus 2013 (83.7%). Per the 2018 guideline, reflex IHC testing was performed on 633 breast cancers (17.8%); the majority of reflex testing results were negative (541 of 633; 85.5%). The overall distribution of HER2 FISH results (per the 2018 guideline) was 88.5% negative and 11.5% positive.
CONCLUSIONS.—: By eliminating the equivocal FISH category, the 2018 ASCO/CAP guideline significantly reduced the HER2 FISH-positive rate in tumors with equivocal (2+) IHC results.
人表皮生长因子受体 2（HER2）检测在乳腺癌中的指南随着时间的推移而不断变化，从美国食品药品监督管理局（FDA）指南到 2007 年、2013 年和 2018 年发布的美国临床肿瘤学会（ASCO）/美国病理学家协会（CAP）指南。
调查 2018 年 ASCO/CAP 指南实施后，通过荧光原位杂交（FISH）对免疫组织化学（IHC）结果为 2+的 HER2 不确定（equivocal）乳腺癌进行 HER2 状态赋值的变化。
该研究纳入了 3556 例 IHC 为 HER2 不确定（2+）的浸润性乳腺癌，在 2018 年 7 月后被送到我们的 FISH 实验室。对于某些被称为 2 组、3 组和 4 组的 FISH 结果，进行了反射性测试（重复 IHC 染色）。根据 2018 年指南的建议，对这些反射性病例进行了 IHC 和 FISH 的同时检查。对 FISH 数据进行了分析，比较了美国 FDA 和 ASCO/CAP 2007、2013 和 2018 年的解释。
在 3548 例具有完整数据的浸润性乳腺癌中，根据不同指南，FISH 的百分比一致性以 ASCO/CAP 2018 与美国 FDA 最高（96.5%），其次是 ASCO/CAP 2018 与 2007 年（93.8%），而 ASCO/CAP 2018 与 2013 年最低（83.7%）。根据 2018 年的指南，对 633 例乳腺癌（17.8%）进行了反射性 IHC 检测；大多数反射性检测结果为阴性（633 例中有 541 例；85.5%）。根据 2018 年的指南，HER2 FISH 结果的总体分布为 88.5%为阴性，11.5%为阳性。
通过消除不确定的 FISH 类别，2018 年 ASCO/CAP 指南显著降低了 IHC 结果为不确定（2+）的肿瘤中 HER2 FISH 阳性率。
