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Molecular Characterization of Inflammatory Myofibroblastic Tumors With Frequent ALK and ROS1 Gene Fusions and Rare Novel RET Rearrangement.

具有高频ALK和ROS1基因融合及罕见新型RET基因重排亚型的炎性肌纤维母细胞肿瘤的分子特征

Antonescu CR,Suurmeijer AJ,Zhang L,Sung YS,Jungbluth AA,Travis WD,Al-Ahmadie H,Fletcher CD,Alaggio R

Abstract

Approximately 50% of conventional inflammatory myofibroblastic tumors (IMTs) harbor ALK gene rearrangement and overexpress ALK. Recently, gene fusions involving other kinases have been implicated in the pathogenesis of IMT, including ROS1 and in 1 patient PDGFRB. However, it remains uncertain whether the emerging genotypes correlate with clinicopathologic characteristics of IMT. In this study, we expand the molecular investigation of IMT in a large cohort of different clinical presentations and analyze for potential genotype-phenotype associations. Criteria for inclusion in the study were typical morphology and tissue availability for molecular studies. The lack of ALK immunoreactivity was not an excluding factor. As overlapping gene fusions involving actionable kinases are emerging in both IMT and lung cancer, we set out to evaluate abnormalities in ALK, ROS1, PDGFRB, NTRK1, and RET by fluorescence in situ hybridization. In addition, next-generation paired-end RNA sequencing and FusionSeq algorithm was applied in 4 cases, which identified EML4-ALK fusions in 2 cases. Of the 62 IMTs (25 children and 37 adults), 35 (56%) showed ALK gene rearrangement. Of note, EML4-ALK inversion was noted in 7 (20%) cases, seen mainly in the lung and soft tissue of young children including 2 lesions from newborns. There were 6 (10%) ROS1-rearranged IMTs, all except 1 presenting in children, mainly in the lung and intra-abdominally and showed a distinctive fascicular growth of spindle cells with long cell processes, often positive for ROS1 immunohistochemistry. Two of the cases showed TFG-ROS1 fusions. Interestingly, 1 adult IMT revealed a RET gene rearrangement, a previously unreported finding. Our results show that 42/62 (68%) IMTs are characterized by kinase fusions, offering a rationale for targeted therapeutic strategies. Interestingly, 90% of fusion-negative IMTs were seen in adults, whereas >90% of pediatric IMT showed gene rearrangements. EML4-ALK inversion and ROS1 fusions emerge as common fusion abnormalities in IMT, closely recapitulating the pattern seen in lung cancer.

摘要

约50%的普通型炎性肌纤维母细胞肿瘤(IMTs)伴ALK基因重排和过表达。近年来,已证明其它激酶的基因融合,如ROS1和PDGFRB,与IMT的发病机制有关。然而这些新出现的基因型是否与IMT的临床病理特征有关仍然未知。本文作者对不同临床表现的IMT大样本进行详细的分子遗传学研究,并分析基因型-表型之间的潜在相关性。本组病例的纳入标准为典型的形态学及足够的组织样本用于分子研究。缺乏ALK免疫表达不是排除因素。由于可控激酶相关性重叠基因融合可同时出现在IMT和肺癌中,作者通过荧光原位杂交技术评估ALK、ROS1、PDGFRB、NTRK1及RET的异常情况。另外,对4例进行了二代RNA序列末端配对测序和融合序列测定,其中2例发现EML4-ALK基因融合。在62例IMTs(儿童25例,成人37例)中,35例(56%)显示ALK基因重排。有7例(20%)出现EML4-ALK倒置,且主要发生于儿童肺和软组织,其中2例发生在新生儿。有6(10%)例IMT出现ROS1重排,除1例外,均发生在儿童患者的肺及腹腔内,形态学显示长梭形细胞呈特征性束状排列,免疫组化ROS1常阳性,其中2例显示TFG-ROS1融合,而1例成人IMT中显示RET基因重排,该发现此前从未见报道。本组结果显示:68%(42/62)的IMTs以激酶融合为特征,为制定靶向治疗策略提供了理论依据。90%融合阴性的IMTs发生在成人,而>90%的儿童IMT显示了基因重排。EML4-ALK倒置和ROS1融合是IMT中融合异常最常出现的,这与肺癌的表现模式极为相似。

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