Clinical History: 
This 35-year-old female presented to clinic complaining of pain and swelling posterior to her right knee of approximately 3 months duration. Physical examination confirmed the presence of a soft tissue mass in the patient’s right posterior lower leg. An MRI scan demonstrated a well-defined oval lesion, confirmed to be a neurofibroma by subsequent surgery.


MR Technique: 
Scans were acquired on a 3 T Siemens Trio Tim MR system. (A) Axial pre-contrast spin echo T1-weighted (TR/TE 614/11 ms, scan time 2:10 min:sec, slice thickness 4 mm) images as well as (B) sagittal turbo spin echo T2-weighted (TR/TE 5400/77 ms, scan time 3:10 min:sec, slice thickness 3 mm) images were obtained, in addition to (C) sagittal post-contrast spin echo fat-saturated T1-weighted images.

Imaging Findings:
A well-defined oval lesion is present posterior to the proximal tibial shaft interposed between the medial and lateral heads of the gastrocnemius muscle and the soleus. This lesion measures 5.5 × 2.9 × 2.4 cm exhibiting low and high signal intensity on T1 and T2-weighted images, respectively. Post-contrast images demonstrate heterogeneous enhancement, particularly peripherally. No adjacent soft tissue edema is appreciated.