Case 19:
Diagnosis please!
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Imaging Diagnosis

Posterior mediastinal mass lesion: neurogenic tumor
Histopath: Schwannoma



Schwannomas or neurilemomas are benign tumors of the peripheral nerves, and make up one-third of neural tumors. Nerve sheath tumors are the most common neurogenic tumors, and are usually benign. These tumors are of nerve sheath or Schwann cell in origin. These tumors grow lateral to the parent nerve.

Neurofibromas are the next most common peripheral nerve tumors and also originate from the Schwann cell. They grow by expanging the parent nerve and are seen in von Recklinghausen’s disease.

Although neurogenic tumors have a similar appearance, certain features do help in differentiating cell type: in children it is likely to be a neuroblastoma or ganglioneuroblastoma that may contain speckled calcification; in an adult it is likely to be a ganglioneuroma (it mat be elongated in the superior to inferior direction), or a schwannoma or neurofibroma (it is likely to be rounded). CT also helps in determining bony erosions or involvement of neural canal/ intra spinal extension (MRI better!).

Calcification does not help determine benign or malignant, and malignant tumors usually have ill-defined borders. On CT, nerve sheath tumors have a lower attenuation than skeletal muscle due to high amount of lipid within these tumors; there may be interstitial fluid or cystic degeneration in larger tumors.