Chen Yun-An, Lai Jyie-Yu, Hsu Chih-Yi, Lien Huang-Chun, Hang Jen-Fan
Department of Pathology, China Medical University Hospital, Taichung, Taiwan.
Taiwan Society of Pathology, Taipei, Taiwan.
Virchows Arch. 2025 Jul 21. doi: 10.1007/s00428-025-04192-5.
BRAF immunohistochemistry (IHC) serves as a surrogate for BRAF p.V600E but shows variable performance across tumor types and institutions. This study evaluated BRAF IHC staining quality and interpretation in general pathology laboratories through a nationwide proficiency test (PT) in Taiwan, focusing on the most commonly encountered thyroid neoplasm and colorectal cancer. This PT was organized by the Taiwan Society of Pathology using a tissue microarray, containing six tumor cores with confirmed BRAF mutation status and one positive control. Participating laboratories performed BRAF IHC staining and interpretation independently, with results centrally reviewed for concordance, accuracy, and staining quality. Twenty-six pathology laboratories participated. Two laboratories failed the initial control check. Among the remaining 24, 17 (70.83%) demonstrated optimal staining, while 5 (20.83%) showed over-staining and 2 (8.33%) under-staining. No significant associations were found between staining quality and antibody clones, platforms, dilution folds, or assay types. Interpretation was highly concordant (100% agreement and accuracy) for tissues with 3 + or negative staining. However, discrepancies arose in tissues with 2 + intensity (50% positive, 41.67% negative, 8.33% equivocal) and 1 + intensity (83.33% disagreement with test results). The overall accuracy was 79.2%, with sensitivity at 58.3% and specificity at 100%. Under-calling was frequent in cases with 1 + staining (33 cores across 23 laboratories) and 2 + staining (3 cores across 3 laboratories). Our study highlights the importance of optimizing staining quality and reinforcing education on interpretation criteria. To minimize false-negative results, we recommend molecular confirmation for all cases exhibiting diffusely weak staining.
BRAF免疫组化（IHC）可作为BRAF p.V600E的替代指标，但在不同肿瘤类型和机构中表现各异。本研究通过台湾的一项全国性能力验证试验（PT），评估了一般病理实验室中BRAF IHC染色质量及判读情况，重点关注最常见的甲状腺肿瘤和结直肠癌。该PT由台湾病理学会组织，采用组织芯片，其中包含六个已确认BRAF突变状态的肿瘤核心及一个阳性对照。参与实验室独立进行BRAF IHC染色及判读，结果由中心统一审核，以评估一致性、准确性和染色质量。共有26家病理实验室参与。两家实验室在初始对照检查中未通过。在其余24家实验室中，17家（70.83%）染色效果最佳，5家（20.83%）染色过度，2家（8.33%）染色不足。染色质量与抗体克隆、平台、稀释倍数或检测类型之间未发现显著关联。对于染色为3+或阴性的组织，判读高度一致（一致性和准确性均为100%）。然而，对于染色强度为2+的组织（50%阳性，41.67%阴性，8.33%不明确）和1+的组织（与检测结果的不一致率为83.33%）出现了差异。总体准确率为79.2%，敏感性为58.3%，特异性为100%。在染色为1+的病例（23家实验室的33个核心）和2+的病例（3家实验室的3个核心）中，漏判情况较为常见。我们的研究强调了优化染色质量及加强判读标准教育的重要性。为尽量减少假阴性结果，我们建议对所有呈现弥漫性弱阳性染色的病例进行分子确认。
