颅内多形性黄色星形细胞瘤的MRI表现及误诊分析

MR imaging features and misdiagnosis analysis of intracranial pleomorphic xanthoastrocytoma

目的探讨颅内多形性黄色星形细胞瘤的MRI特点并分析误诊原因。方法回顾性分析12例经病理证实的颅内PXA的临床、病理及影像学资料。结果肿瘤均位于幕上,9例部位表浅,与脑膜关系密切,但仅3例见脑膜强化。瘤体呈多房囊性伴壁结节8例,呈实性伴囊变4例。实性成分与正常脑灰质信号相比,T1WI呈等或稍低信号,T2WI呈等或稍高信号;囊性成分与脑脊液相比,FLAIR呈稍高信号。FLAIR示11例轻-中度瘤周血管源性水肿。7例接受DWI,实性部分6例呈等或稍高信号,1例呈明显高信号。3例接受MRS检查,瘤体实性部分胆碱/肌酐(Cho/Cr)升高,N-乙酰天门冬氨酸/肌酐(NAA/Cr)降低,1例见脂质(lip)峰。增强后瘤体实性部分明显强化,其中不均匀强化7例,均匀强化5例。8例术前误诊,分别诊断为胚胎发育不良性神经上皮肿瘤(2例)、脑膜瘤(1例)、间变性星形细胞瘤(1例)、血管母细胞瘤(1例)、节细胞胶质瘤(2例)、脉络丛乳头状瘤(1例)。结论 PXA临床罕见,与胚胎发育不良性神经上皮肿瘤、脑膜瘤等影像表现相似,术前易误诊,结合MR功能成像有助于鉴别诊断。

Objective To evaluate MRI features of pleomorphic xanthoastrocytoma（PXA）and to analyze causes of misdiagnosis.Methods The clinical,pathological and imaging findings of 12 pathologically confirmed PXA were retrospectively analyzed.Results All the neoplasms were supratentorial and superficial in location with obvious leptomeningeal contact in nine cases,but only three cases showed leptomeningeal enhancement.Eight cases were predominantly cystic with enhanced mural nodules.Four cases were predominantly solid mass that showed some cystic changes.The solid lesions showed isointense or slightly hypointense relative to gray matter on T1 WI,isointense or slightly hyperintense on T2 WI.Cystic areas showed hyperintense relative to cerebrospinal fluid on FLAIR.Eleven cases had mild or moderate vasogenic edema on FLAIR.Tumor nodules were markly hyperintense in only one case,slightly-hyperintense or isointense in six cases on DWI.Proton magnetic resonance spectrum of three patients showed Cho/Cr increasing and NAA/Cr decreasing.One case showed lip peak.After contrast administration,solid components of seven tumors enhanced heterogeneously and five cases enhanced homogeneously.Eight cases was misdiagnosised,including dysembryoplastic neuroepithelial tumor（n=2）,meningiomas（n=1）,anaplastic astrocytoma（n=1）,hemangioblastoma（n=1）,gangliogliomas（n=2）and choroid plexus papilloma（n=1）.Conclusion PXA is a rare glioma and presents similar to dysembryoplastic neuroepithelial tumor,meningiomas or other tumors.Combining imaging features with functional MRI may contribute to differential diagnosis.