Objective: To investigate the characteristics of RET gene rearrangement revealed by fluorescence in situ hybridization (FISH) in lung cancer. Methods: A total of 616 formalin-fixed paraffin-embedded surgical samples from lung adenocarcinomas with wild-type EGFR gene and no ALK protein expression by immunohistochemistry obtained at Peking Union Medical College Hospital, Beijing, China between December 2019 and April 2022 were included. Thirty-three tumors with RET gene rearrangement determined by imbalanced-based reverse-transcription droplet digital PCR (RT-ddPCR) were analyzed using break-apart FISH. The results were confirmed, and RET gene fusion variants were identified through next generation sequencing (NGS). Results: RET gene rearrangements were found in all 33 RET RT-ddPCR positive cases via NGS, including 27 cases of KIF5B::RET, 3 CCDC6::RET, 2 ERC1::RET and 1 CCDC186::RET rearrangements. Moreover, 32 RET positive and 1 RET negative cases were defined using FISH. Among the RET FISH-positive cases, 25 (78.1%, 25/32) showed break-apart FISH signal pattern in 52%-100% of tumor cells with the rearrangement and 7 cases (21.9%, 7/32) presented isolated 3' signal type in 38%-88% positive tumor cells. There was no RET-positive case with single 5' pattern in the cohort. The most common partner gene was KIF5B (81.8%, 27/33). Most of the patients with RET gene rearrangement were female (72.7%, 24/33). Conclusion: RET FISH-positive lung cancer is commonly characterized by a high proportion of rearrangement cancer cells and break-apart FISH signal type.
目的： 探讨肺癌中RET基因重排肿瘤的荧光原位杂交（FISH）信号特征。 方法： 收集北京协和医院2019年12月至2022年4月存档的甲醛固定石蜡包埋的表皮生长因子受体（EGFR）野生型和间变性淋巴瘤激酶（ALK）免疫组织化学阴性的肺腺癌标本616例，经基于不平衡设计的逆转录数字PCR方法筛选出RET阳性的标本33例，以分离探针进行RET FISH检测，并通过二代测序验证FISH结果和确定RET基因重排类型。 结果： 在33例逆转录数字PCR检出的RET阳性样本中，经二代测序检测均含有RET基因重排。其中包括27例KIF5B：：RET、3例CCDC6：：RET、2例ERC1：：RET和1例CCDC186：：RET重排。RET FISH检测结果为32例阳性、1例阴性。在FISH阳性标本中，25例（78.1%，25/32）样本为红绿信号分离，阳性细胞数为52%~100%；7例（21.9%，7/32）样本以孤立的3′信号为特征，阳性细胞数介于38%~88%之间。未见以单个5′信号聚集为特征的FISH阳性类型。最常见的伙伴基因是KIF5B（81.8%，27/33），且RET基因重排者女性居多（72.7%，24/33）。 结论： 对于RET基因重排的肺癌来说，大多数样本的FISH类型表现为分离信号，而且具有重排信号的瘤细胞常是高占比的。.