[Comparison of the methods for detecting NTRK gene fusion variations in papillary thyroid carcinoma].

Objective: To investigate the frequency of neurotrophic tyrosine receptor kinase (NTRK) gene variations in papillary thyroid carcinoma (PTC) and to analyze the feasibility of detecting tropomyosin receptor kinase (TRK) proteins using immunohistochemistry (IHC) to predict the fusion variation of NTRK. Methods: A cohort of 848 PTC cases was collected at the Department of Pathology, Shenzhen People's Hospital from June 2017 to June 2020. The expression levels of TRK proteins were detected using IHC in 848 PTC samples, and the DNA-based next generation sequencing (NGS) was performed to detect NTRK rearrangements in 150 PTCs. Results: There were 242 males and 606 females, with an age range of 9-83 years. In 120 cases with TRK expression detected by IHC, 13 cases were confirmed to harbor a NTRK gene fusion by NGS. The frequency of NTRK fusion in PTC was 1.5% (13/848). The sensitivity and specificity of TRK-IHC positivity for screening NTRK fusion in PTC were 100% and 21.9%, respectively. The specificity of weak-, moderate- and strong-positive stains of TRK IHC were 23.8%, 76.9% and 93.8%, respectively. The specificity of NTRK gene fusion was predicted to increase with the enhanced intensity of IHC staining. In BRAF V600E negative PTC samples, the specificity of weak-and moderate-positive stains of TRK IHC increased to 62.5% and 96.8%, respectively. Seven NTRK fusion partners were found in the PTC, including EML4, ETV6, CDH1, GJD2, TPR, TFG and SQSTM1. Conclusions: There is a low variation frequency of NTRK gene fusion in PTC. TRK IHC can be used as a screening method for NTRK fusion variation in PTC. The specificity of TRK IHC predicting NTRK fusion can be further enhanced by increasing the cutoff value of the positive cell number and staining intensity of TRK-IHC staining, or being combined with BRAF V600E negativity.目的： 探讨甲状腺乳头状癌（papillary thyroid carcinoma，PTC）中NTRK基因变异频次，分析免疫组织化学法检测TRK蛋白预测NTRK基因融合变异的可行性。 方法： 收集2017年6月至2020年6月深圳市人民医院病理科存档的848例PTC组织样本，其中男性242例，女性606例，患者年龄范围9~83岁。利用免疫组织化学检测848例PTC组织中TRK的表达情况；利用基于DNA的下一代测序检测150例PTC中NTRK融合变异。 结果： 免疫组织化学检测TRK阳性病例120例，下一代测序检测发现NTRK融合病例13例，PTC中NTRK融合频次为1.5%（13/848）。免疫组织化学检测PTC中NTRK融合的灵敏度和特异度分别为100%和21.9%，免疫组织化学检测弱阳性、中等阳性和强阳性的特异度分别为23.8%、76.9%、93.8%；预测NTRK基因融合的特异度随免疫组织化学染色强度增加而增加；在BRAF V600E阴性的样本中，免疫组织化学检测TRK弱阳性和中等阳性的特异度提升至62.5%和96.8%。下一代测序检测出EML4、ETV6、CDH1、GJD2、TPR、TFG和SQSTM1 7种融合伴侣基因。 结论： PTC中存在较低的NTRK基因变异频次；免疫组织化学检测TRK可用作PTC中NTRK融合变异的筛查方法；提高免疫组织化学染色阳性细胞数阈值、染色强度或结合BRAF V600E阴性检测结果可进一步提高检测的特异度。.