Department of General Thoracic Surgery, Juntendo University School of Medicine, Tokyo, Japan.
PLoS One. 2013 Aug 1;8(8):e69794. doi: 10.1371/journal.pone.0069794. Print 2013.
EML4-ALK fusion gene is found in only a small subset (2-6%) of non-small cell lung cancer. There is an urgent need to establish a rational diagnostic algorithm to identify this rare but important fusion in lung cancer.
We performed a comprehensive analysis of EGFR/KRAS mutation and ALK rearrangement in a total of 360 surgically resected lung cancers. ALK rearrangement was examined by 3 analyses: multiplex reverse transcription-PCR, fluorescent in situ hybridization (FISH), and immunohistochemistry (IHC) with the intercalated antibody-enhanced polymer method. A scoring system was used for IHC (iScore). A test set (202 patients with unselected lung cancer) was used for proposing a diagnostic algorithm. This diagnostic algorithm was validated in 158 patients with EGFR and KRAS mutation-negative adenocarcinoma.
ALK rearrangement was identified in 2 patients (1.0%) from the test set and both adenocarcinomas were negative for EGFR and KRAS mutations. The results of FISH and RT-PCR were completely matched. The highest iScore 3 was found only in the 2 positive cases. A diagnostic algorithm was proposed: IHC screening for ALK rearrangement followed by confirmatory FISH. In the validation set, 8 cases (5.1%) had iScore 3 and were positive for FISH, while the other cases had iScore 0 and were negative for FISH.
Screening for ALK rearrangement by IHC followed by confirmatory FISH is a rational diagnostic algorithm. If needed, patients may be selected for screening ALK rearrangement by their EGFR and KRAS mutation status.
EML4-ALK 融合基因仅存在于一小部分（2-6%）非小细胞肺癌中。因此，需要建立一个合理的诊断算法来识别这种罕见但重要的肺癌融合。
我们对总共 360 例手术切除的肺癌进行了 EGFR/KRAS 突变和 ALK 重排的综合分析。通过 3 种分析方法检测 ALK 重排：多重逆转录-PCR、荧光原位杂交（FISH）和免疫组化（IHC），使用插入抗体增强聚合物方法。采用评分系统进行 IHC（iScore）分析。使用 202 例未经选择的肺癌患者的测试集提出诊断算法。该诊断算法在 158 例 EGFR 和 KRAS 突变阴性的腺癌患者中得到验证。
在测试集中发现 2 例（1.0%）患者存在 ALK 重排，且这两例腺癌均为 EGFR 和 KRAS 突变阴性。FISH 和 RT-PCR 的结果完全匹配。只有在这 2 例阳性病例中发现最高的 iScore 3。提出了一种诊断算法：首先进行 ALK 重排的 IHC 筛选，然后进行 FISH 确认。在验证集中，8 例（5.1%）患者的 iScore 3 为阳性，且 FISH 阳性，而其他病例的 iScore 0 为阴性，且 FISH 阴性。
通过 IHC 进行 ALK 重排的筛选，然后进行 FISH 确认是一种合理的诊断算法。如有需要，可根据 EGFR 和 KRAS 突变状态选择患者进行 ALK 重排筛查。
