Mediastinum > Schwannoma

Schwannoma (Neurilemmoma):

View cases of schwannoma


Schwannoma is the most common neurogenic tumor of the posterior mediastinum. The lesion arises from the nerve root sheath, extrinsically compresses the nerve fibers, and extends along the intercostal nerve [3]. Lesions that arise from the vagus, phrenic, or internal mammary nerves are located in the more anterior aspects of the mediastinum. It is generally a benign, slow growing tumor of a peripheral nerve which is usually encapsulated. Most patients are asymptomatic, but they may have radicular pain. Treatment is surgical and resection is curative. Malignant schwannomas are rare (2% of cases, although slightly more common in patients with NF1) and are characterized by rapid growth and local invasion, distant metastases are uncommon. Patients with malignant lesions are more likely to present with chest pain.


On CT the lesion appears as a low density, sharply marginated, soft tissue, posterior mediastinal mass typically in the para-spinous portion. There may be intra-spinal extension producing a "dumbbell" lesion in about 10% of cases. The lesion is usually round, or elongated in a horizontal direction following the intercostal nerve. There may be pressure erosion of the adjacent bony structures. Small foci of calcification have been reported in up to 10% of cases and this may primarily be in a peripheral pattern [3]. If large, the lesion may be inhomogeneous or cystic due to areas of hemorrhage and necrosis within the mass.

A "split fat" sign refers to fat attenuation around the soft tissue mass caused by displaced, but intact surrounding fat that covers the neuromuscular bundle, indicative of a noninfiltrating underlying neurogenic mass [3].

On MRI, schwannomas have low to intermediate signal on T1 images, and intermediate to high signal on T2 images [3]. The solid components of the lesion will enhance with gadolinium administration [3].

(1) Chest 1997; Strollo DC, et al. Primary mediastinal tumors. Part II: Tumors of the middle and posterior mediastinum. 112: 1344-57

(2) Radiographics 2003; Rha SE, et al. Neurogenic tumors in the abdomen: tumor types and imaging characteristics. 23: 29-43

(3) AJR 2016; Pavlus JD, et al. Imaging of thoracic neurogenic tumors. 207: 552-561

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