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● Clinical Presentation ● 临床表现 ● A 50-year-old man with back pain. ● 50岁男性，背部疼痛。
● Further Work-up ● 进一步检查 ● See Images at Left ● 看左边的图片
● Imaging Findings ● 影像表现 ● Click on Annotated Thumbnail to reveal caption ● 点击缩略图显示注释
● 1A - Annotated Caption ● 1A - 注释说明 ● (A) Frontal chest radiograph demonstrates a large, well-circumscribed mass in the left upper chest (arrow). There is no evidence of rib destruction. ● （A）正位胸部X片显示左上胸部有一个大的、边界清楚的肿块（箭头）。没有肋骨破坏的证据。
● 2B - Annotated Caption ● 2B - 注释说明 ● (B) Lateral chest radiograph confirms the smooth inferior margin of the mass (arrow); however, the precise location of the abnormality cannot be determined. ● （B）侧位胸部X片显示肿块的下缘光滑（箭头）；但是，无法精确定位。
● 3C - Annotated Caption ● 3C -注释说明 ● (C) Noncontrast computed tomography (soft-tissue windows) shows that the mass has heterogeneous density. It forms obtuse margins with the pleura, suggesting an extrapulmonary location (arrow). ● （C）非增强计算机断层扫描（软组织窗口）显示肿块具有不均匀密度。它与胸膜形成钝角边缘，提示位于肺外（箭头）。
● 4D - Annotated Caption ● 4D -注释说明 ● (D) T2-weighted magnetic resonance imaging (MRI) shows that the mass has heterogeneous but predominantly high signal intensity and multiple hypointense septa (arrow). ● （D）T2加权磁共振成像（MRI）显示肿块信号不均匀，主要为高信号并多发低信号间隔（箭头）。 ● Differential Diagnosis ● 鉴别诊断 ● Schwannoma: More than 90% of posterior mediastinal masses are neurogenic in origin. The smooth margins and signal characteristics favor a nerve sheath tumor. Cystic spaces can be intermixed within the tissue, resulting in high signal intensity on T2-weighted MRI. Adjacent osseous erosion and remodeling would be expected, however. ● 神经鞘瘤：超过90％的后纵隔肿块源于神经源性。平滑的边缘和信号特征倾向诊断神经鞘瘤。组织内混合囊性成分，导致T2加权MRI上的高信号。可能可见相邻骨质的吸收和重塑。 ● Meningocele: A meningocele is a nonenhancing cystic mass. It should mimic the density and intensity of cerebral spinal fluid. Enlargement of the neural foramen and contiguity with the thecal sac are expected. ● 脊膜膨出：脊膜膨出是一种不强化的囊性肿块。它类似于脑脊液的密度和强度。会扩大神经孔并与神经囊连接。 ● Lymphoma: Additional intrathoracic lymphadenopathy would be expected. Signal intensity on T2-weighted MRI is variable. High signal on T2-weighted MRI may represent active disease, inflammation, cystic change, or immature fibrosis. ● 淋巴瘤：可能另外会有的胸内淋巴结肿大。T2加权MRI上的信号强度是可变的。T2加权MRI上的高信号可能代表活动性疾病、炎症、囊变或不成熟纤维化。 ● Essential Facts ● 基本事实 ● Schwannomas arise from the nerve sheath and consist of Schwann cells in a collagenous matrix. ● 神经鞘瘤起源于神经鞘并且由胶原基质中的施万细胞组成。 ● They are also called neurinomas or neurilemmomas. ● 它们也被称为神经瘤或神经鞘瘤。 ● They have a true capsule. ● 他们有一个真被囊。 ● The mass is eccentric to the affected nerve. ● 肿块与受累神经偏心生长。 ● Schwannomas are the most common intradural extramedullary mass. ● 神经鞘瘤是最常见的髓外硬膜下肿块。 ● They are typically solitary; multiple schwannomas are seen in neurofibromatosis type 2. ● 他们通常是孤立的；在神经纤维瘤病2型中可见多发神经鞘瘤。 ● When symptomatic, they usually present with pain associated with movement. ● 当出现症状时，他们通常伴随着与运动有关的疼痛。 ● They typically demonstrate intense enhancement. ● 他们通常表现出明显强化。 ● They often cause enlargement of the intervertebral foramen. ● 它们经常导致椎间孔扩大。 ● Up to 15% have a dumbbell appearance, with both intra- and extradural elements. ● 高达15％有哑铃外观，是由于同时具备硬膜内和硬膜外成分。 ● Calcification is seen in 10%. ● 10％的患者出现钙化。 ● A schwannoma may be difficult to distinguish from a neurofibroma. ● 神经鞘瘤可能难以与神经纤维瘤区分。 ● Schwannomas are more likely to have a visible capsule and intratumoral cysts. ● 神经鞘瘤更有可能出现明显的被膜和肿瘤内囊变。 ● The Carney complex consists of melanotic schwannomas, cutaneous myxomas, cardiac myxomas, and adrenal tumors. ● Carney综合征由黑素瘤神经鞘瘤、皮肤粘液瘤、心脏粘液瘤和肾上腺肿瘤组成。 ● Other Imaging Findings ● 其他影像表现 ● No Other Imaging Findings ● 没有其他影像表现 ● Pearls and Pitfalls ● 经验与教训 ● The target sign on T2-weighted MRI (high signal intensity peripherally and low signal centrally) is seen more frequently in neurofibromas than in schwannomas. ● T2加权MRI上的靶征（周围高信号强度和中央低信号）在神经纤维瘤中比在神经鞘瘤中更常见。 ● The visualization of fascicular bundles in neurogenic tumors is known as the fascicular sign. ● 神经源性肿瘤呈束状的外观称束征。 ● Melanotic schwannomas show high signal intensity on T1-weighted images. ● 黑色素神经鞘瘤在T1加权像上显示高信号强度。 ● The target and fascicular signs are typically seen in benign lesions, although they have been described in malignant peripheral nerve sheath tumors. ● 靶征和束体通常见于良性病变，尽管它们也有在恶性周围神经鞘瘤中被描述。 ● Further Readings ● Beaman FD, Kransdorf MJ, Menke DM. Schwannoma: radiologic-pathologic correlation. Radiographics. 2004;24(5):1477-1481. 来源：医学影像家园 |
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