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Abstract：
Neurofibromatosis type 1 (NF1) is an autosomal dominant syndrome caused by germline alteration of the NF1gene. Among various NF1-related manifestations, obstructive hydrocephalus especially in adult NF1 cases is less frequently found. We report two adult NF1 cases exhibiting obstructive hydrocephalus due to an aggressive posterior fossa tumor exhibiting pathological characteristics of pilocytic astrocytoma as NF1-related manifestations. In these two cases, we performed endoscopic third ventriculostomy (ETV) and tumor biopsy as an initial treatment. The initial pathological diagnosis of the tumor is conventional pilocytic astrocytoma. After biopsy both cases revealed rapid tumor growth, therefore, we performed tumor removal, chemotherapy, and radiation therapy during an aggressive clinical course. However, both cases revealed dismal prognosis due to the progression of the tumor in spite of successful management of hydrocephalus by an initial ETV. DNA methylation analysis revealed that the tumor of one case matched high-grade astrocytoma with piloid features (HGAP). Most central nervous system tumors developed in NF1 are less aggressive such as pilocytic astrocytoma; however, recently a few studies revealed that HGAP, which has been a newly introduced malignant tumor in the World Health Organization Classification of Tumors of the Central Nervous System, 5th edition (WHO CNS 5), rarely develops in NF1 cases. These findings suggested that HGAP might be one of the important causes of obstructive hydrocephalus in adult NF1 cases.
摘要：
1型神经纤维瘤病（NF1）是由NF1基因的种系改变引起的常染色体显性综合征。在各种与NF1相关的表现中，尤其是在成人NF1病例中，阻塞性脑积水的发生率较低。我们报告了两例成年NF1病例，由于侵袭性后颅窝肿瘤表现出毛细胞星形细胞瘤的病理特征为NF1相关表现，因此表现出阻塞性脑积水。在这两种情况下,我们进行了内镜下第三脑室造瘘术(ETV)和肿瘤活检作为初始治疗.肿瘤的最初病理诊断是常规的毛细胞星形细胞瘤。活检后，两个病例都显示肿瘤快速生长，因此,我们做了肿瘤切除,化疗,在积极的临床过程中进行放射治疗。然而,尽管最初的ETV成功治疗了脑积水，但由于肿瘤进展，这两个病例均显示预后不佳。DNA甲基化分析显示，1例肿瘤与具有毛样特征（HGAP）的高级星形细胞瘤相匹配。NF1中发生的大多数中枢神经系统肿瘤的侵袭性较低，例如毛细胞星形细胞瘤；然而，最近一些研究表明，HGAP，它是世界卫生组织中枢神经系统肿瘤分类中新引入的恶性肿瘤，第5版（WHOCNS5），很少在NF1病例中发展。这些发现表明，HGAP可能是成人NF1病例中阻塞性脑积水的重要原因之一。
