Fisher Kevin E, Cohen Cynthia, Siddiqui Momin T, Palma John F, Lipford Edward H, Longshore John W
Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA.
Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA.
Hum Pathol. 2014 Nov;45(11):2281-93. doi: 10.1016/j.humpath.2014.07.014. Epub 2014 Aug 7.
Malignant melanoma patients require BRAF mutation testing prior to initiating BRAF inhibitor therapy. Molecular testing remains the diagnostic gold standard, but recent work suggests that BRAF immunohistochemistry (IHC) confers comparable results. Sample attributes and scoring criteria that may affect BRAF IHC interpretation, however, are poorly defined. We investigated formalin-fixed, paraffin-embedded samples with variable challenging interpretative attributes: metastases, core needle biopsies, sample tissues less than 60 mm(2), samples with greater than 50% necrosis, and/or samples with greater than 10% melanin pigmentation. Three pathologists independently scored 122 BRAF V600E IHC-labeled melanoma samples for percentage (0%-100%) of staining intensity (0-3+). Interscorer BRAF IHC discrepancies were resolved by consensus review. Lenient (≥1+, >0%) and stringent (≥2+, ≥10%) IHC scoring criteria were compared to BRAF V600 mutation (cobas) results (n = 118). Specimens with greater than 10% melanin pigmentation and metastatic samples produced the majority of interobserver IHC and IHC/cobas scoring discrepancies. Consensus review using stringent scoring criteria decreased the number of discrepant results, yielded very good interobserver reproducibility, and improved specificity and positive predictive value for BRAF p.V600E detection. BRAF p.V600K mutations accounted for 57.1% of false-negative IHC results when stringent, consensus criteria scoring were used. The cobas test detected 75.0% (8/12) of BRAF IHC-negative BRAF p.V600K mutations confirmed by next-generation sequencing. Molecular BRAF testing is the preferred screening test for BRAF inhibitor therapy eligibility because of superior sensitivity in challenging interpretative melanoma specimens. However, BRAF V600E IHC has excellent specificity and positive predictive value when stringent, consensus scoring criteria are implemented. To decrease IHC scoring discrepancies, pathologists should interpret metastatic and pigmented samples with caution.
恶性黑色素瘤患者在开始BRAF抑制剂治疗前需要进行BRAF突变检测。分子检测仍然是诊断的金标准，但最近的研究表明，BRAF免疫组织化学（IHC）能提供可比的结果。然而，可能影响BRAF IHC解读的样本属性和评分标准定义不明确。我们研究了福尔马林固定、石蜡包埋的样本，这些样本具有各种具有挑战性的解读属性：转移灶、粗针活检样本、小于60平方毫米的样本组织、坏死率大于50%的样本和/或黑色素沉着率大于10%的样本。三名病理学家独立对122个BRAF V600E IHC标记的黑色素瘤样本的染色强度百分比（0%-100%）（0-3+）进行评分。评分者之间的BRAF IHC差异通过共识审查解决。将宽松（≥1+，>0%）和严格（≥2+，≥10%）的IHC评分标准与BRAF V600突变（cobas）结果（n = 118）进行比较。黑色素沉着率大于10%的样本和转移样本产生了大多数观察者间IHC和IHC/cobas评分差异。使用严格评分标准的共识审查减少了差异结果的数量，产生了非常好的观察者间可重复性，并提高了BRAF p.V600E检测的特异性和阳性预测值。当使用严格的共识标准评分时，BRAF p.V600K突变占IHC假阴性结果的57.1%。cobas检测在下一代测序确认的BRAF IHC阴性BRAF p.V600K突变中检测出75.0%（8/12）。由于在具有挑战性的解读性黑色素瘤样本中具有更高的敏感性，分子BRAF检测是BRAF抑制剂治疗资格的首选筛查检测。然而，当实施严格一致的评分标准时，BRAF V600E IHC具有出色的特异性和阳性预测值。为了减少IHC评分差异，病理学家在解读转移样本和色素沉着样本时应谨慎。
