软组织神经鞘肿瘤的MRI诊断

MRI diagnosis of nerve sheath tumors in soft tissue

目的评价MR平扫及动态增强扫描对软组织神经鞘肿瘤的诊断价值。方法回顾分析23例30个经病理证实软组织神经鞘肿瘤的MRI特征,其中15个良性神经鞘肿瘤,包括许旺瘤(神经鞘膜瘤)13个(12例),神经纤维瘤2个(2例);15个为恶性外周神经鞘肿瘤。23例均行常规MR扫描,包括自旋回波(SE)T1WI,快速自旋回波(FSE)T2WI以及快速多平面扰相梯度回波序列(FMPSPGR)平扫和动态增强扫描。结果(1)23例患者共30个病灶,软组织神经鞘肿瘤表现为梭形(15个),靶征(9个),神经出入征(10个),脂肪分离征(10个);2个(2例)恶性神经鞘膜肿瘤显示周围水肿。(2)12个良性神经鞘肿瘤中9个表现为延迟强化,3个无明显强化或轻度强化;所有15个恶性外周神经鞘肿瘤及3个良性神经鞘肿瘤表现为第1期明显或中度强化,第2期和第3期持续强化或强化程度稍有下降。结论梭形肿块、靶征、与神经关系密切及脂肪分离征是软组织神经鞘肿瘤较特征性的表现,而肿瘤的MR动态增强强化方式和周围有无水肿对神经鞘肿瘤良、恶性鉴别有一定价值。

Objective To evaluate MRI and dynamic enhancement scanning in the diagnosis of nerve sheath tumors （ NSTs ） in soft tissue. Methods Thirty histopathologieally proved soft-tissue NSTs were analyzed by MRI in 23 patients. They were divided into 15 benign NSTs which included 13 Schwannomas, 2 neurofibromas and 15 malignant peripheral nerve sheath tumors（MPNSTs）. Scan sequences included SE T1WI, FSE T2WI, Fast multiplanar spoiled gradient recalled technique （FMPSPGR） before and after injection of Gd-DTPA. Results There were 30 NSTs in 23 patients. Soft-tissue NSTs presented as an fusiform mass（15/30） ,“target” signs（9/30） , the tubular entering and exiting nerve （10/30） , the splitfat sign （10/30）. Two MPNSTs showed associated surrounding edema. Twelve benign NSTs manifested delayed enhancement（n =9）and no enhancement（n = 3）. All MPNSTs and 3 benign NSTs demonstrated early enhancement with slow washout or without obvious washout. Conclusion Fusiform shape, “target” sign, the relationship to the nerve and “split-fat” sign were characteristic signs of soft-tissue NSTs and dynamic contrast-enhanced MRI may be useful and helpful to differentiate malignant from benign NSTs.