Presentation
Lower back pain 3 months ago and left sciatica. Accidentally discovered pelvic mass on the previous lumbosacral spine MRI study.
Patient Data
A well-circumscribed globular mass lesion is seen located in the left presacral space. It measures about 7.0 x 6.8 x 6.0 cm along its CC & axial dimensions respectively. It shows an inhomogeneous signal in T2 WI with intrinsic necrotic and cystic changes which returns a bright signal on T2 WI "target sign". The lesion abuts the posterior pelvic floor muscles, and scallops bone posteriorly. It is likely separable from the posterior uterine wall and splays the adjacent rectum with a clear plane of cleavage in between.
The mass is intimately related to the left S1 exiting nerve root through its extraforaminal course.
Case Discussion
Left presacral mass lesion, likely of perineural origin. MR features suggest pelvic schwannoma.