The appearances are in keeping with a benign intradural extramedullary spinal tumor.
The differential includes; a spinal meningioma, schwannoma and neurofibroma.
No convinving dural tail is evident, however this is the most likely cause, 80% of spinal meningiomas occuring at the thoracic level.
No internal cystic component as is common with a schwannoma. No other lesions to suggest a neurofibroma.