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患者，男，17岁。反复发作的顽固性癫痫10余年 
胚胎发育不良性神经上皮肿瘤(dysembryoplastic neuroepithelial tumor,DNET)属于神经元与神经胶质混合肿瘤,WHOI级,约占神经上皮来源肿瘤的1%及药物难治性癲痫的87%。1993年WHO首次独立分类。病理学特点为以脑皮质为基底的多发结节状结构,局部脑体积膨大,80%伴脑皮质发育不良,因此也有作者认为DNET并非真性肿瘤。目前尚未发现与基因突变有关,但CD34染色阳性表明其与干细胞异常有关。镜下显示胶质神经元成分,多发少突样细胞构成的柱状或结节状与皮质垂直,这些柱状结构附近可见“漂浮”于白色黏液样基质的神经元。免疫组织化学染色GFAP(+),MIB-1为0%~8%。DNET好发于儿童与青年,绝大多数于20岁前发病,以药物难治性癫痫为特征,其他症状包括认知力下降,但一般无局部神经功能障碍。本病生长缓慢,几乎不恶变。手术切除即可治愈,一般不复发。
Dysembryoplastic neuroepithelial tumor (DNET) is a kind of neuron-glial mixed tumor with WHOI grade, accounting for about 1% of tumors originated from neuroepithelium and 87% of drug-resistant epilepsy. WHO was first classified independently in 1993. Pathological features were multiple nodular structures based on cerebral cortex, local cerebral volume enlargement and 80% hypoplasia of cerebral cortex. Therefore, some authors believed that DNET was not a true tumor. No gene mutation has been found to be involved, but positive CD34 staining has been linked to stem cell abnormalities. Microscopically, glial neuron components are shown, with columns or nodules of polyoligodendroid cells perpendicular to the cortex. Near these columns are neurons 'floating' in a white mucinous matrix. Immunohistochemical staining showed that GFAP(+) and MIB-1 were 0%~8%. DNET tends to occur in children and young people, and most of them come on before the age of 20. It is characterized by drug-resistant epilepsy. Other symptoms include cognitive decline, but there is generally no local neurological dysfunction. This disease grows slowly, hardly evil change. Surgical excision can cure, do not recur commonly.①少突胶质细胞的出现是DNET最具诊断意义的特征,它常围绕毛细血管分布呈腺泡状或菊形团状结构,缺乏神经元周围卫星现象,细胞核呈圆形或椭圆形, 核周有空晕,呈“鱼眼”样,胞质少,细胞形态较一致;②黏液样基质,少突胶质细胞和少量星形细胞间的基质呈黏液样,稀疏处形成多个微囊, 有时可见成熟的神经元如“浮蛙”一样漂浮其中, 从而构成特异的胶质神经元结构;③DNET的组织病理学上肿瘤呈多结节状结构分布于皮层,由特异性胶质神经元成分混合而成,包括少突胶质细胞样细胞、星形细胞和漂浮其中的成熟神经元,各成分比例变化很大,以少突胶质细胞样细胞为主;CT肿瘤呈近似球形的低密度灶,界限清晰析,边缘不规则,占位效应不明显,病灶周围水肿较轻,20%病灶可见斑片样钙化,有时可伴有出血灶,位于大脑凸面的肿瘤因生长缓慢致颅骨内板受压变薄,增强扫描无强化。CT tumors show approximately spherical low-density lesions with clear boundaries, irregular edges, and no obvious space-occupying effect. Edema around the lesions is relatively mild, with patchy calcification visible in 20% of the lesions, sometimes accompanied by hemorrhagic lesions. Tumors located on the convex surface of the brain become thinner due to slow growth, which results in compression of the internal skull plate.MRI病灶内见多发结节样和假囊性结构,典型的MRI征象为三角征、多囊、分叶状或瘤内分隔。“三角征”的形成可能与神经胶质纤维通路放射状分布有关,瘤内分隔可能与肿瘤分叶状表现有关。T1WI呈低信号,信号强度略高于脑脊液,T2WI可见囊性或多囊性“肥皂泡”样结构,呈高信号。典型的DNET在T2WI上信号往往高于一般的肿瘤,类似囊性病灶,T2- FLAIR多表现为高信号或高等混杂信号,因此常被描述为假囊肿病变边缘可见线样、斑片样或环形更高信号带,即“环形征”,具有诊断特异性,可能与肿瘤边缘围绕含胶质一神经元成分的疏松组织有关。部分病变可见附壁结节,信号强度略高于大脑皮质。增强扫描少部分病变内或边缘可见线样、斑片样、结节样或环形强化,系增生的神经胶质细胞伴血管增生所致。有学者认为,DNET的强化与否和病理类型有关,单纯型DNET很少有强化,而复杂型DNET可出现强化。DNET的结节状强化或小环形强化往往非常规则,这与其他肿瘤强化方式明显不同,可作为其MRI特征之一。Multiple nodular and pseudocystic structures were observed in MRI lesions. Typical MRI signs were triangulation, polycystic, lobulated or intratumoral septum. The formation of 'triangulation' may be related to the radial distribution of the glial fiber pathway, and the intratamoral division may be related to the lobulated appearance of the tumor. T1WI shows low signal intensity, which is slightly higher than CSF, and T2WI shows high signal with cystic or multi-cystic 'soap bubble' -like structure. Typical DNET on T2WI signal is often higher than the common tumors, similar cystic stove, T2 - FLAIR more performance as high or higher mixed signals, thus is often described as false cyst lesions edge visible line sample, or circular patch sample with higher signal, namely the 'circular', has the specificity, may be related to the tumor edge around the loose organization containing colloid ingredient a neuron. Mural nodules can be seen in some lesions, with signal strength slightly higher than that of the cerebral cortex. Enhancement scan showed linear, patchy, nodular or circular enhancement in a small number of lesions or edges, which were caused by hyperplasia of glial cells with vascular hyperplasia. Some scholars believe that the enhancement of DNET is related to the pathological type. Simple DNET has little enhancement, while complex DNET can be enhanced. The nodular or small ring enhancement of DNET is often very regular, which is significantly different from other tumor enhancement methods and can be used as one of its MRI features.儿童和青年患者,临床表现为难治性癫痫发作,病史较长,具有典型的影像学特点有助于DNET的诊断。影像学特点包括CT扫描似球形低密度病灶,边界清晰,边缘不规则,占位效应不明显,如有斑片样钙化、出血灶有助于DNET诊断。MRI病灶内见多发结节样和假囊性结构,呈三角征、多囊、分叶状或瘤内分隔,病变边缘呈“环形征”具有诊断特异性,结节状强化或小环形强化往往非常规则,这与其他肿瘤强化方式明显不同,可作为其MR特征之一。由于DNET常误诊,所以鉴别诊断尤为重要,应注意与位于皮层和皮层下的囊性肿瘤、带附壁 结节的肿瘤(如节细胞胶质瘤、多形性黄色瘤型星形细胞瘤、毛细胞型星形细胞瘤和少突胶质细胞瘤)相鉴别。Children and young adults with a long history of refractory epileptic seizures with typical imaging characteristics that may be helpful in the diagnosis of DNET. Imaging features include spherical low-density lesions in CT scan, clear boundaries, irregular edges, and no obvious mass effect. For example, patchy calcification and hemorrhagic lesions are helpful for DNET diagnosis. Multiple nodular and pseudocystic structures were observed in MRI lesions, presenting triangulation, polycystic, lobulated or intratumoral separation. The lesion margin presented 'ring sign' with diagnostic specificity, and nodular or small ring enhancement was often very regular, which was significantly different from other tumor enhancement methods and could be regarded as one of MR features. Because DNET is often misdiagnosed, differential diagnosis is particularly important, and should be distinguished from cystic tumors located in the cortex and subcortex, and tumors with mural nodules (e.g., ganglion glioma, xanthoma multiforme astrocytoma, hair cell astrocytoma, and oligoglioma). 少突胶质细胞瘤多为白质起源,早期累及皮质,病灶较大,占位效应及水肿明显,常早期侵入蛛网膜下腔,肿瘤包绕脑膜血管。Oligodendroglioma is mostly of white matter origin, involving cortex in the early stage, with large lesion, obvious space occupying effect and edema, often invading subarachnoid space in the early stage, and surrounding meningeal vessels.节细胞胶质瘤常位于皮层及皮层下区,好发于颞叶,与DNET鉴别存在困难。Ganglion gliomas are usually located in the cortex and subcortical areas and tend to occur in the temporal lobe.蛛网膜囊肿和表皮样囊肿蛛网膜囊肿和表皮样囊肿为脑外病变,具有脑外占位的征象如皮质受压、蛛网膜下腔増宽等。同时,蛛网膜囊肿一般张力较大,信号与脑脊液一致,可与DNET相鉴别。表皮样囊肿DWI呈高信号有助于鉴别。Arachnoid cysts and epidermoid cysts are extracerebral lesions with signs of extracerebral space occupation such as cortical compression and subarachnoid space enlargement. At the same time, arachnoid cyst general tension larger, signal and cerebrospinal fluid consistent, can be identified with DNET phase. High DWI signal of epidermoid cyst is helpful for identification.毛细胞型星形细胞瘤好发于儿童,小脑半球多见,呈囊实性,实性部分明显强化。pilocytic astrocytomas are more common in children and more common in cerebellar hemispheres.
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