MR findings in primary retroperitoneal schwannoma

To evaluate the MR findings in primary retroperitoneal schwannoma.

Seven cases of primary retroperitoneal schwannoma, in whom the diagnosis was confirmed histopathologically, were analyzed retrospectively. The following items were reviewed at MR imaging: tumor diameter, margin, homogeneity, signal intensity as compared to normal renal parenchyma, presence/absence of infiltration into adjacent organs, and, in 1 and 4 cases, the enhancement on Gd-dynamic images and post-contrast T1-weighted images, respectively.

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 regular in all of the benign cases and irregular in the malignant one. The malignant case showed infiltration into the liver and duodenum. Four of the benign 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 mixed 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-weighted 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.

On MR imaging, primary retroperitoneal schwannomas show different signal intensity characteristics, including cystic degeneration. There are, however, no specific characteristics of these tumors.