MRI diagnosis of nerve sheath tumors in soft tissue

Objective: To evaluate MRI and dynamic enhancement scanning in the diagnosis of nerve sheath tumors (NSTs) in soft tissue. Methods: Thirty histopathologically proved soft-tissue NSTs were analyzed by MRI in 23 patients. They were divided into 15 benign NSTs which included 13 Schwannomas, 2 neurofibromas and 15 malignant peripheral nerve sheath tumors (MPNSTs). Scan sequences included SET1WI, FSE T2WI, Fast multiplanar spoiled gradient recalled technique (FMPSPGR) before and after injection of Gd-DTPA. Results: There were 30 NSTs in 23 patients. Soft-tissue NSTs presented as an fusiform mass (15/30), 'target' signs (9/30), the tubular entering and exiting nerve (10/30), the split-fat sign (10/30). Two MPNSTs showed associated surrounding edema. Twelve benign NSTs manifested delayed enhancement (n=9) and no enhancement (n=3). All MPNSTs and 3 benign NSTs demonstrated early enhancement with slow washout or without obvious washout. Conclusion: Fusiform shape, 'target' sign, the relationship to the nerve and 'split-fat' sign were characteristic signs of soft-tissue NSTs and dynamic contrast-enhanced MRI may be useful and helpful to differentiate malignant from benign NST. (authors)