摘要
目的：探讨幕上原始神经外胚层肿瘤（PNET）的常规MRI、MR扩散加权成像（DWI）特征及其病理基础。方法：对经病理证实的15例幕上PNET患者，分析肿瘤的常规MRI、DWI表现及病理资料。定量测定肿瘤实质和对侧正常脑白质区表观扩散系数（ADC）的值，采用配对t检验比较两者平均ADC值的差异。结果：肿瘤多数位于大脑皮层下，平均最大直径5.7cm。肿瘤多呈类圆形和分叶状、边界清晰。肿瘤实质在T1WI呈稍低信号或中等信号；T2WI呈中等信号或稍高信号。13例肿瘤内见不同程度的坏死囊变区，2例肿瘤内见小点片状出血。增强扫描肿瘤实质不同程度的强化，肿瘤周围无明显水肿或水肿较轻；1例肿瘤沿脑脊液播散，1例肿瘤沿室管膜播散。DWI上7例肿瘤实质呈不均匀性等高信号，4例呈较均匀性高信号，ADC图上9例肿瘤实质呈低信号，2例呈稍低信号。肿瘤实质的平均ADC值为0.72×10-3mm2/s，对侧正常脑白质区的平均ADC值为0.86×10-3mm2/s。肿瘤实质较其对侧正常脑白质区的平均ADC的差异有统计学意义（t=10.84，P<0.05）。病理上肿瘤细胞较小，呈圆形或椭圆形，细胞核染色深，核分裂象多见，细胞浆少，界限不清；肿瘤细胞排列密集，呈束状或巢片状分布。免疫组化肿瘤细胞表示神经元分化的突触素阳性，表示胶质细胞分化的胶质纤维酸性蛋白阳性，多数肿瘤有神经元、胶质细胞双潜能分化。结论：幕上PNET的病理基础决定其在常规MRI、DWI的特征性表现，肿瘤实质在DWI表现为高信号和ADC值减低，与其密集的细胞构成及细胞核与细胞浆比值高有关。
Abstract
Objective: To investigate the conventional MRI, diffusion-weighted imaging(DWI) characteristics of supratentorial primitive neuroectodermal tumors(PNET) and correlate them with pathological findings. Methods: Fifteen patients with supratentorial PNET were confirmed pathologically, the conventional MRI, DWI features and pathological data of supratentorial PNET were analyzed. The apparent diffusion coefficient(ADC) values from the solid portion of tumor and the normal contralateral white matter were measured quantitatively, statistical analysis was performed with two sample t-test. Results: Most tumors were localized in cerebral subcortex, the mean maximum diameter of tumor was 5.7cm. Most tumors were presented as round or lobulated masses with well-demarcated margins. The solid portion of tumors showed slightly hypointense to isointense on T1WI, and isointense to slightly hyperintense on T2WI. Different cystic and necrotic portions within tumors were found in 13 patients, focal intratumoral hemorrhage were found in 2 patients. The tumors showed enhancement after contrast medium injection. Mild peritumoral edema was present. Ependymal or cerebrospinal dissemination was noted in 2 patients. On DWI, the solid portion of tumors showed heterogeneous isointense to hyperintense in 7 patients, homogeneous hyperintense in 4 patients, On ADC map, the solid portion of tumors showed hypointense in 9 patients, slightly hypointense in 2 patients. The average ADC values of the solid portion of tumors was 0.72×10-3mm2/s. The average ADC values of the normal contralateral white matter was 0.86×10-3mm2/s. There was statistically significant difference in mean ADC value between the solid portion of tumors and normal contralateral white matter（t=10.84，P<0.05）. On microscopic examination, the cellular tumors composed of round to oval small cells with hyperchromatic nuclei and frequent mitoses, the cytoplasm of tumor cells were scanty and ill-defined, The tumor cells were densely packed and arranged in cords or nests. Immunohistochemically, tumor with neuronal differentiation was reactive for synaptophysin(Syn), tumor with glial differentiation was reactive for glial fibrillary acidic protein(GFAP), most tumors exhibited both neuronal and glial bi-potential differentiation. Conclusions: The pathology of supratentorial PNET determine its characteristic appearance on conventional MRI and DWI, the hyperintensity on DWI and decreased ADC value within the solid portion of tumors is caused by their dense cellularity and high nuclear to cytoplasmic ratio.
关键词
脑肿瘤 /
神经外胚瘤 /
原始 /
外周 /
磁共振成像
Key words
Brain neoplasms /
Neuroectodermal tumors /
primitive /
peripheral /
Magnetic resonance imaging
季学满;张宗军;卢光明;印洪林;袁彩云;张志强.
幕上原始神经外胚层肿瘤的MR扩散加权成像与病理学分析[J]. 中国临床医学影像杂志. 2009, 20(9): 673-676
JI Xue-man;ZHANG Zong-jun;LU Guang-ming;YIN Hong-lin;YUAN Cai-yun;ZHANG Zhi-qiang.
Diffusion-weighted magnetic resonance imaging features and pathological analysis ofsupratentorial primitive neuroectodermal tumors[J]. Journal of China Clinic Medical Imaging. 2009, 20(9): 673-676
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