MR IMAGING CRITERIA FOR TUMOR RECURRENCE FOLLOWING WIDE EXCISION OF EXTREMITY SOFT-TISSUE SARCOMA

1. Discrete mass -Intermediate to slightly high signal (relative to skeletal muscle)on T1W, high on T2W. Administration of I.V. contrast is helpful in distinguishing fluid containing proteinaceous material (intermediate to high signal intensity on T1W images) from solid tumor recurrence (intermediate to high signal intensity on T1W image). First post-operative MRI should be obtained about three months after surgery.
   
   
2. Contour deformity should be viewed with suspicion. Ultrasound can be obtained for confirmation or exclusion and percutaneous aspiration as necessary. Sonogram is difficult to interpret first three months following surgery.
   
   
3. 'Feathery' areas of high signal intensity on T2W and on post contrast MR image generally do not indicate recurrence.
   
   
4. If there is very high signal intensity on T2W but shape and contour of muscle is maintained on T1W, it generally indicates post therapy change.
   
   
5. Post contrast fat suppression sequence may overestimate degree of edema or other abnormality. It may be useful to evaluate subcutaneous tissue recurrence. Fast spin-echo T2W images with fat suppression accentuates post surgical changes.
   
   
6. When in doubt, contrast material can be utilized.
   
   
7. Fluid collections (seromas) are common following wide local excision of tumors of the thigh. Post surgical hematoma may also occur.