MR findings in primary retroperitoneal Schwannoma

Objective: To evaluate the MR findings in primary retroperitoneal schwannom a. Material and Methods: Seven cases of primary retroperitoneal schwannoma, in whom the diagnosis was confirmed histopathologically, were analyzed retros pectively. The following items were reviewed at MR imaging: tumor diameter, margin, homogeneity, signal intensity as compared to normal renal parenchy ma, presence/absence of infiltration into adjacent organs, and, in 1 and 4 cases, the enhancement on Gd-dynamic images and post-contrast T1-weighted i mages, respectively. Results: Tumor diameter was 5.5+/-3.1 cm, ranging from 2.5 to 10 cm in the 6 benign schwannomas. and 12 cm in 1 malignant. The tumor margin was regula r in all of the benign cases and irregular in the malignant one. The malign ant case showed infiltration into the liver and duodenum. Four of the benig n schwannomas showed a homogeneous, and 2 presented a heterogeneous pattern , while the malignant schwannoma was heterogeneous. On T1-weighted images, the benign schwannomas were hypointense in 4 cases, isointense in 1 and mix ed in 1, while on T2-weighted images, they were hyperintense in 5 and mixed in 1. The malignant case showed mixed intensity on both T1- and T2-weighte d images. On enhanced T1-weighted images, capsular, septal enhancement was noted in 2 cases, overall enhancement in 2, and, on Gd-dynamic images, late enhancement was shown. Conclusion: On MR imaging, primary retroperitoneal schwannomas show differe nt signal intensity characteristics, including cystic degeneration. There a re, however, no specific characteristics of these tumors.