Retroperitoneal schwannomas in the anterior pararenal space: dynamic enhanced multi-slice CT and MR findings

To evaluate the imaging features of schwannomas in the anterior pararenal space (APS), especially focusing on dynamic enhanced multi-slice CT (MSCT) and MR findings.

Eight patients with pathologically proved retroperitoneal schwannomas in the APS underwent dynamic enhanced multi-slice CT (MSCT), while three of these patients also had a contrast-enhanced MR examination. The imaging findings were retrospectively reviewed.

All eight cases exhibited forward displacement of the pancreas, and three cases showed lateral displacement and compression of the inferior vena cava. The tumors had round or oval shape with a maximal axial diameter of 4.0–12.3 cm (average, 6.7 cm). All eight tumors were solitary and well circumscribed. Of the eight retroperitoneal schwannomas in the APS, six exhibited a capsule with thickness of 1.0–2.0 mm, one showed punctate calcification, two displayed cystic degeneration, and three revealed a “target sign” on CT and MR. The tumors were hypo-dense on unenhanced CT images, hyper-intense on T2W images, and homogeneously hypo-intense on T1W images. All eight tumors exhibited gradual enhancement on dynamic enhanced CT or MR images. One case showed delayed enhancement. Heterogeneous enhancement was the dominant pattern occurring in seven out of eight tumors.

The imaging findings of schwannoma in the APS correspond with its pathological composition. Schwannoma should be included in the differential diagnosis of tumors in the APS.