대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Malignant Nerve Sheath Tumor of the Mediastinum

Radiologic Findings

Chest radiograph shows a huge mass on the right lung and associated pleural effusion. CT shows that the mass is probably arising from middle mediastinum and growing and compressing the right lung. It looks encapsulated and contains multiple cystic portions. Large amount of pleural effusion is seen. MR images show intermediated signal intensity of the mass on T1-weighted image, heterogeneous enhancement after contrast administration, and bright signal intensity on T2-weighted image. Note the cystic portions that are dark on T1WI and bright on T2WI and not enhanced by contrast material.

Brief Review

Neurogenic tumors account for about 9% of primary mediastinal masses in adults. In mediastinal neurogenic tumors of adults, more than 75% are nerve sheath tumors. Malignant nerve sheath tumors, termed malignant schwannoma, are relatively uncommon, but represent up to 15% of nerve sheath tumors. They may cause pain and are usually associate with neurofibromatosis. The CT diagnosis of malignancy can be difficult. Although benign tumors tend to be small, sharply marginated and fairly homogeneous in attenuation, and malignant nerve sheath tumors tend to be large, infiltrating, irregular, and inhomogeneous, these findings are not sufficiently reliable to obviate histologic evaluation. When localized, it is not possible to distinguish benign from malignant tumors. Destruction of bone appears to be a sign of malignant invasion. Pleural effusion is a sign of malignant tumor. Malignant tumors may show metastatic foci in the pleura or lungs. In a study of eight cases of malignant schwannoma arising in the thorax, tumors averaged nine centimeters in diameter and six showed areas of low attenuation caused by necrosis, but only three had an irregular edge and five had a smooth margin. Both benign and malignant lesions may be symptomatic, rendering clinical differentiation of limited utility. Calcification and some degree of contrast opacification may be present with either benign or malignant tumors. Lung metastases may be present.

References

1. Naidich DP, Webb WR, Muller NL, et al. Computed tomography and magnetic resonance of the thorax, 3rd ed. Philadelphia: Lippincott-Raven, 1999: 143-148
2. Armstron P, Wilson AG, Dee P, et al. Imaging of disease of the chest, 3rd ed. London: Mosby, 2000:829-837
3. Moon WK, Im IJ, Han MC. Malignant schwannomas of the thorax: CT findings. J Comput Assist Tomogr 1993; 17:274-276

Keywords

Mediastinum, Malignant tumor,