Department of Diagnostic Pathology, Kurume University Hospital, Kurume, Japan.
Department of Diagnostic Pathology, Kurume University Hospital, Kurume, Japan.
J Thorac Oncol. 2015 May;10(5):800-805. doi: 10.1097/JTO.0000000000000507.
The standard diagnostic method for echinoderm microtubule-associated protein-like 4-anaplastic lymphoma receptor tyrosine kinase translocation is fluorescence in situ hybridization (FISH). Recently, immunohistochemistry (IHC) has been reported as a potential method in screening for anaplastic lymphoma kinase (ALK)-positive non-small-cell lung carcinomas (NSCLC), whereas several authors have reported a discordance between FISH and IHC results. We investigated the heterogeneity of ALK gene rearrangement in excision specimens by FISH and also examined whether the FISH score of ALK gene rearrangement corresponded in excision and biopsy samples from the same patient.
Twenty ALK IHC-positive patients including six patients treated with crizotinib therapy were evaluated for the presence of ALK FISH. For evaluation of heterogeneity of ALK gene rearrangement in excision specimens, we defined six to 10 observation areas in each case, and the number of ALK FISH positive observation areas (≥15% rearrangement detected) was investigated. ALK FISH score in small biopsy samples was classified as positive (≥15% rearrangement detected), equivocal (5-14% rearrangement detected), or negative (<4% rearrangement detected).
Of a total of 64 tumor observation areas from nine excision specimens, 50 areas were positive for ALK gene rearrangement (81.8%). In the comparison of excision and small biopsy samples, all excision specimens were ALK FISH-positive (100%; 6 of 6), whereas only three of the small biopsy samples in these patients were positive (50%; 3 of 6), two were equivocal (33%; 2 of 6), and one was negative (17%; 1 of 6). The two equivocal patients received crizotinib and showed a response.
ALK gene rearrangement heterogeneity was observed in NSCLC specimens by FISH. Our findings suggested that IHC-positive/FISH-equivocal cases should not be considered true "false-negatives" when a small biopsy sample was used for ALK analysis.
棘皮动物微管相关蛋白样 4-间变性淋巴瘤激酶受体酪氨酸激酶易位的标准诊断方法是荧光原位杂交（FISH）。最近，免疫组织化学（IHC）已被报道为筛选间变性淋巴瘤激酶（ALK）阳性非小细胞肺癌（NSCLC）的一种潜在方法，然而，一些作者报告了 FISH 和 IHC 结果之间的不一致。我们通过 FISH 研究了 FISH 阳性的 20 例 ALK 免疫组化患者中 ALK 基因重排的异质性，并检查了同一患者的切除和活检样本中 ALK 基因重排的 FISH 评分是否一致。
评估了 20 例 ALK IHC 阳性患者（包括 6 例接受克唑替尼治疗的患者）是否存在 ALK FISH。为了评估切除标本中 ALK 基因重排的异质性，我们在每个病例中定义了 6 到 10 个观察区，并研究了 ALK FISH 阳性观察区的数量（≥15%检测到的重排）。ALK FISH 评分在小活检样本中被分类为阳性（≥15%检测到的重排）、可疑（5-14%检测到的重排）或阴性（<4%检测到的重排）。
在 9 个切除标本的 64 个肿瘤观察区中，有 50 个区存在 ALK 基因重排（81.8%）。在切除和小活检样本的比较中，所有切除标本均为 ALK FISH 阳性（100%；6/6），而这些患者的小活检样本中只有 3 个阳性（50%；6/6），2 个可疑（33%；6/6），1 个阴性（17%；6/6）。两名可疑患者接受了克唑替尼治疗，并显示出了反应。
通过 FISH 观察到 NSCLC 标本中存在 ALK 基因重排异质性。我们的研究结果表明，当使用小活检样本进行 ALK 分析时，IHC 阳性/FISH 可疑的病例不应被视为真正的“假阴性”。
