Introduction
Identification of genetic alterations in central nervous system (CNS) tumors provides diagnostic and prognostic information and allows identification of potential therapeutic targets. Next-generation sequencing (NGS) technologies currently used for molecular testing are costly and remain largely limited to major academic centers or reference labs. Identification of histologic or immunohistochemical correlates for particular molecular alterations can serve as surrogates and can help triage cases for subsequent NGS-based confirmation. Recently, adult IDH-wildtype adult glioblastomas (GBMs) with fibroblast growth factor receptor (FGFR) gene alterations were reported to show palisading monomorphic cells, delicate arcuate vasculature, and microcalcifications. We explored whether pediatric tumors with FGFR fusion also show these histologic features and whether these features could predict the presence of this gene alteration.

Material and methods
We reviewed pediatric CNS tumors with FGFR-fusions to retrospectively determine the presence/absence of the above-mentioned histological features in fusion-positive tumors.

Results
10 pediatric tumors with FGFR fusions were identified. Pediatric tumors demonstrated histologic and tumor type diversity, with diagnoses of pilocytic/pilomyxoid astrocytoma, pediatric-type oligodendroglioma, anaplastic astrocytoma, polymorphous low-grade neuroepithelial tumor of the young, rosette-forming glioneuronal tumor, and extraventricular neurocytoma.

Conclusions
Pediatric FGFR-fused CNS tumors demonstrate histologic features similar to their adult counterparts but also exhibit significant morphologic variability. As such, this histologic variability prevents the prediction of FGFR fusion and necessitates molecular testing for the identification of this alteration.



中文翻译：

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伴有 FGFR 改变的小儿中枢神经系统肿瘤的组织学特征

介绍
中枢神经系统 (CNS) 肿瘤基因改变的鉴定提供诊断和预后信息，并允许鉴定潜在的治疗靶点。目前用于分子测试的新一代测序 (NGS) 技术成本高昂，并且在很大程度上仍仅限于主要学术中心或参考实验室。特定分子改变的组织学或免疫组织化学相关性的鉴定可以作为替代物，并有助于对病例进行分类，以进行后续基于 NGS 的确认。最近，据报道具有成纤维细胞生长因子受体 (FGFR) 基因改变的成人 IDH 野生型成人胶质母细胞瘤 (GBM) 显示栅栏状单形细胞、精致的弓状脉管系统和微钙化。

材料和方法
我们回顾了 FGFR 融合的儿科 CNS 肿瘤，以回顾性确定融合阳性肿瘤中上述组织学特征的存在/不存在。

结果
鉴定出 10 个具有 FGFR 融合的儿科肿瘤。小儿肿瘤表现出组织学和肿瘤类型的多样性，诊断为毛细胞/毛粘液样星形细胞瘤、小儿型少突胶质细胞瘤、间变性星形细胞瘤、年轻的多形性低级别神经上皮肿瘤、玫瑰花结型神经元肿瘤和脑室外神经细胞瘤。

结论
小儿 FGFR 融合的 CNS 肿瘤表现出与成人相似的组织学特征，但也表现出显着的形态学变异性。因此，这种组织学变异性阻止了 FGFR 融合的预测，并且需要进行分子测试来识别这种改变。