대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Intercostal Schwannoma

Radiologic Findings

Chest radiograph shows left paraspinal mass in lower T-spine level.

CT scans show a homogeneous low attenuation mass in left paraspinal area with mild enhancement. Splaying of left lower ribs with cortical thickening is noted.

The mass is well encapsulated and highly vascularized. The outer surface is smooth, the cut surface shows grayish yellow homogeneous, flesh and slightly fibrotic nature.

Brief Review

Almost all intrathoracic nerve sheath tumors arise either from the intercostal or sympathetic nerves, the rare exceptions being neurofibromas or schwannomas of the phrenic or vagus nerves. Many arise adjacent to the spine and in about 5% of cases, extend through the neural foramina into the spinal canal (the so-called “dumbell tumor”)(1). Tumors arising from the intercostal nerves can result in rib erosion, notching, and sclerosis because of their arising adjacent to bone and growing slowly. They can cause pressure erosions of adjacent ribs and vertebrae ? an important diagnostic feature.

On plain radiographs, nerve sheath tumors typically appear as sharply marginated round, elliptical, or lobulated paravertebral masses, and tend to be limited to one or two interspaces in length. Associated rib or vertebral deformity or enlargement of a neural foramen is visible in about 50% of cases. Nerve sheath tumors may also be seen in the middle or anterior mediastinum, occurring in relation to the vagus, phrenic, or recurrent laryngeal nerve, or along the courses of intercostal nerves(2).

On CT, nerve sheath tumors typically appear as well-marginated, smooth, round or elliptical masses. Enlargement of neural foramina may be better shown on CT than on plain films. In over 70% of cases, peripheral nerve or nerve sheath tumors appear to be lower in attenuation than chest wall muscle; in the remainder, they are of soft-tissue attenuation. Variable enhancement of the tumor may be seen following contrast infusion; peripheral enhancement is common. Small areas of calcifications are seen in 5% to 10%.

On MR imaging, neurogenic tumors usually have low to intermediate signal intensity on T1-weighted images and inhomogeneously high signal intensity on T2-weighted images. Schwannomas often have peripheral higher signal intensity on T2-weighted images, maybe due to myxoid degeneration.

References

1. Hansell DM, Armstrong P, Lynch DA, McAdams HP. Imaging of diseases of the chest, 4th ed. Elsevier: Mosby 2005:951-958.

2. Webb WR, Higgins CB. Thoracic Imaging, Lippincott Williams & Wilkins 2005:262-266.

Keywords

Chest wall, Benign tumor,