This lesion was a pathologically proved neurofibroma.

Neurogenic tumors may be classified into three groups arising from (a) peripheral nerves or a nerve sheath (neurofibroma or neurilemmoma), (b) sympathetic ganglia (ganglioneuroma or neuroblastoma), and (c) paraganglionic cells (pheochromocytoma or chemodectomas). Tumors in each of these groups may be benign or malignant ^1,4.

Nerve sheath tumors are the commonest posterior mediastinal masses ⁴.

Neurofibroma is one of the benign peripheral nerve sheath tumors that usually affects young patients 20-40 years (range is 16-66 years), with no sex predilection ^1,3,9,10. 

Types of neurofibroma ^3,9:

• localized neurofibroma
  • accounts for 90% of all neurofibromas, usually fusiform tumor, presenting as a painless mass, its usual location is along the superficial cutaneous nerves, occasionally along deep-seated larger nerves
• diffuse neurofibroma
  • poorly defined lesion within subcutaneous fat, infiltrating along connective tissue septa, inseparable from normal nerve tissue, frequently in subcutaneous tissues of head and neck and presenting as a plaque-like elevation of skin. In 90% of cases, it is not associated with type 1 neurofibromatosis
• plexiform neurofibroma
  • involvement of a long segment of nerve and its branches extending into adjacent muscle, fat or subcutaneous tissue, usually affect nerve plexus or multiple fascicles in a medium-to-large-sized nerves. It is pathognomonic for type 1 neurofibromatosis

Radiologically, neurofibroma appears a well-defined paravertebral mass (usually at cervicothoracic region and usually more than 2 vertebrae long) presenting round or oval shape and with extramedullary location with possible extradural extension. It can be dumbbell-shaped, that is, partially inside and partially outside the spinal canal. In such cases, the intervertebral foramen may be enlarged, and it may be associated with scalloping of the dorsal margin of vertebral body or rib space widening. Although it is frequently of soft-tissue attenuation, they can be of low attenuation because of the presence of fat or fluid (low attenuated paravertebral mass was described to be characteristic for neurofibroma). Some punctate calcification may be also seen. CT after injection of myelography contrast medium may be useful in demonstrating intraspinal extension ^{1,3-5, 7-9}.

On MRI, it appears as low-to-intermediate signal on T1WI, slightly-high-to-high signal on T2WI and FST2WI, usually show moderate to prominent gadolinium contrast enhancement. High signal on T2WI and gadolinium contrast enhancement can be heterogeneous in large lesions. It may show nodules with high signal surrounding a central region of low signal referred to as a "target sign" ^3,5,9-10.

Neurofibromas and schwannomas often cannot be differentiated by imaging. The most helpful signs are: (a) target sign (in neurofibromas and not in schwannomas), (b) pattern of enhancement (central in neurofibromas and diffuse in schwannomas), (c) fascicular appearance, and a T2 hyperintense rim (in schwannomas and not in neurofibromas) ^6,7