FIG 1. A 44-year-old man with right low back pain.

T1-weighted (A, -B) (TR/TE/acquisition, 716/13/2) and T2-weighted (C) (TR/TE/acquisition, 4000/114/2) axial MR images show a large mass (asterisks) in the right paravertebral space at the L4-L5 level. It is isointense to muscle with T1 weighting (A, -B) and isointense to subcutaneous fat and hyperintense to muscle with T2 weighting (C). The mass infiltrates the adjacent structures (arrowheads) with focal erosion of the superior articular process of L5 (arrow). Ipsilateral neural foraminal widening and displacement of the thecal sac due to the epidural component are also demonstrated. Contrast-enhanced T1-weighted (D) (TR/TE/acquisition, 716/13/2) axial MR images reveal moderate homogeneous enhancement of the mass.