病理与临床特点
室管膜下瘤( subependymoma,SE)是一种罕见、生长缓慢的良性肿瘤, Schenker于 1945 年首次命名,属于室管膜来源肿瘤,WHOI 级。2016年 WHO新分类中室管膜肿瘤( ependymal tumors)的其他肿瘤包括黏液乳头型室管膜瘤、室管膜瘤、RELA 融合阳性室管膜瘤与间变性室管膜瘤,后者为WHOⅢ级。SE约占室管膜肿瘤的8%。SE起源于多潜能的室管膜-星形细胞的前体细胞。病理学上肿瘤含有室管膜细胞和星形细胞,其中星形细胞占50%。镜下为簇状细胞核埋入致密的胶质细胞纤维基质中,常伴小囊腔形成,核分裂偶见或无。瘤细胞核形态一致,类似于管膜下胶质细胞,偶见多形核。易见小而融合的囊腔及钙化与出血。肿瘤微血管可增生,偶见细胞突起围绕于血管周围,形成假菊形团,此时可诊断为混合性室管膜瘤/室管膜下瘤。本病可见于各年龄段,但好发于中老年,85%以上超过 15岁,男性较多。临床表现与肿瘤所在部位有关,常出现脑积水。
Subependymoma (SE) is a rare, slow-growing benign tumor, Schenker was first named in 1945, belongs to ependymal source tumor,WHOI grade. In 2016 the WHO classification of ependymal tumor (ependymal tumors) of other tumors including mucous nipple ependymoma, ependymoma, a positive RELA fusion ependymoma and anaplastic ependymoma, which is a category WHO Ⅲ. SE accounted for about 8% of ependymal tumors. SE originates from the pluripotent ependymal precursor of astrocytes. Pathologically, the tumor contains ependymal cells and astrocytes, 50% of which are astrocytes. Microscopically, the nuclei are clustered into a dense glial fibrous matrix, often accompanied by the formation of small cysts, with or without nuclear division. The tumor nuclei are uniform, similar to subtubular glial cells, with occasional polymorphisms. Small fused lumens, calcification, and hemorrhage are common. Tumor microvessels may proliferate, with occasional cellular protuberances surrounding blood vessels to form pseudochrysanthemum masses. At this point, mixed ependymoma/subependymoma can be diagnosed. The disease can be seen in all age groups, but often occurs in the elderly, more than 85% over 15 years old, more male. Clinical manifestations are associated with the location of the tumor, often hydrocephalus.
CT与 MRI 特点
①部位及形态:肿瘤可以发生于脑室通路的任何位置,第四脑室下份最常见(占 50%~60%),其次为侧脑室额角近透明隔处,其他包括第三脑室、桥小脑角区等处。极少数发生于脑实质内。肿块常单发,边界清楚,呈圆形结节状或分叶状,占位征象和水肿通常相对较轻。肿瘤一般小于2cm,少数可瘤体巨大、充满整个脑室。肿瘤较大时易钙化、出血及囊变;
(1) location and morphology: tumor can occur in any location of ventricular pathway, the fourth ventricle is the most common part (accounting for 50%~60%), followed by the lateral ventricle frontal horn near the transparent septum, other areas including the third ventricle, cerebellopontine horn area. Very few occur in the brain parenchyma. The mass is usually solitary, well-defined, nodular or lobulated, and the signs of mass and edema are usually relatively mild. Tumors are generally less than 2cm, and a few can be large and fill the entire ventricle. It is easy to calcify, bleed and cystic change when the tumor is large.
②CT上多为等或稍低密度,囊变为低密度,钙化及瘤内出血为高密度;
(2) on CT, most of them had equal or slightly lower density, and the bursa became low density, calcification and intratumoral hemorrhage were high density.
③MR检查T1WI上多表现为等信号或略低信号,肿瘤内可见多个小囊状低信号区,个别有较大的囊状低信号区。病理学上囊状低信号区富含黏液。T2/ FLAIR上肿瘤呈不均匀高信号。但一般无瘤周水肿。T2*WI及 SWI 显示肿瘤内钙化呈低信号。由于肿瘤血供较差,且血脑屏障相对完整,增强扫描多数无明显强化,少数轻中度强化。DWI无扩散受限,MRS显示Cho正常、Cr相对较高、NAA降低。
(3) MR examination on T1WI showed equal signal or slightly low signal. There were several small cystic low signal areas in the tumor, and some large cystic low signal areas. Pathologically, the saccular-like low signal areas are rich in mucus. The tumor on T2/ FLAIR presents uneven hyperintensity. But generally there is no peritumor edema. T2*WI and SWI showed low signal of calcification in the tumor. Due to the poor blood supply of the tumor and the relatively complete blood-brain barrier, most of the enhanced scans had no obvious enhancement, and a few had mild to moderate enhancement. DWI diffusion was limited,MRS showed normal Cho, relatively high Cr, and reduced NAA.
鉴别诊断
发病部位不同的SE需与不同疾病鉴别。
①室管膜瘤,与绝大多数脑室内肿瘤血运丰富不同的是,管膜下瘤血运不丰富,一般不强化,另一个重要特点是此瘤极少向脑室壁以外的脑实质扩展,即局限于室内,而室管膜瘤易侵犯邻近脑实质;
(1) ependymoma, and the vast majority of intraventricular tumors rich in blood supply is different, the submeningeal tumor blood supply is not rich, generally not enhanced, another important feature is that this tumor rarely to the brain outside the wall of the ventricle parenchyma expansion, that is, confined to the indoor, and ependymoma easy to invade the adjacent brain parenchyma;
②脑室内转移瘤,有原发肿瘤病史,常位于脉络丛,强化显著;
(2) intraventricular metastatic tumor, with a history of primary tumor, often located in choroid plexus, with significant enhancement;
③中神经细胞瘤,侧脑室体部最常见,典型者多发小泡状囊变即泡泡状,常见于青年女性;
(3) nerve cell tumor, lateral ventricle body is the most common, the typical multiple small vesicular cystic change that is bubble-shaped, common in young women;
④脉络丛乳头状侧脑室体部多见,呈分叶状,强化明显。
简要讨论
室管膜下瘤为室管膜来源肿瘤之一,特点是位于脑室内乏血供肿瘤,第四脑室下部最常见,可伴钙化，一般无强化。因本病少见,常需与脑室内其他肿瘤鉴别。
Subependymoma is one of the ependymal source tumors, characterized by intraventricular hypovascular tumor, the most common in the lower part of the fourth ventricle, accompanied by calcification, usually without enhancement. Because this disease is rare, often need to differentiate with cerebral ventricle other tumor.
