MRI Findings of Peripheral Schwannoma: Pathologic Correlation

ABSTRACT

PURPOSE: To characterize the MRI appearance of the peripherally located schwannoma as compared with pathologic findings. MATERIALS AND METHODS: 11 cases of 13 lesions of the schwannoma confirmed by pathology were analyzed, retrospectively. T11 T2 and Gadolinium-enhanced T1 weighted sagittal and axial images were obtained. The signal intensity, contour of lesion, and relationship with surrounding tissue were analyzed. All cases were correlated with MRI and pathologic findings. RESULTS: In 9 out of the 11 cases, schwannoma was connected to the main nerve trunk. Among them, tumors were located centrally in 6 cases and eccentrically in 3 cases. MR findings of schwannoma were iso signal intensity on T1WI(8 cases) with muscle intensity, high signal intensity on T2WI(all cases), strong heterogenous enhancement in all cases. 8 cases showing heterogenous appearance on T2WI, showed mixture of Antoni-A and B area and multifocal hemorrhage. Central low and peripheral high signal intensity on T2Wl(Target sign) was mainly high cellular component in the central portion and diffuse myxoid degeneration at the periphery, pathologically. Reversed target appea.rance(central high, peripheral low on T2WI) revealed central cystic degeneration with low cellular component and hemorrhage in the central portion, and high cellular component at the periphery. Linear band-like low signal intensity on T2WI, suggesting capsule of the schwannoma, was not the true capsule proven by pathology. Thin true capsule was not visualized on T2WI. CONCLUSION: MR appearance of schwannoma was non-specific. The signal intensity on T2 weighted MR imaging was determined by the presence of multifocal hemorrhage, focal cystic and myxoid degeneration, admixture of Antoni-A and B area.