MR-IMAGING OF BENIGN SOFT-TISSUE MASSES OF THE FOOT AND ANKLE

Approximately 75% of all biopsy-proved soft-tissue masses of the foot and ankle are benign tumors or nontumoral lesions representing a varie ty of histologic types. In some cases,it may be difficult if not impos sible to identify the lesion; however, careful analysis of the magneti c resonance (MR) imaging findings and correlation of these findings wi th the patient's clinical history can usually suggest a more specific diagnosis, particularly in the most common benign tumors of the foot ( eg, fibromatosis, cavernous hemangioma) and in nonneoplastic soft-tiss ue lesions such as Morton neuroma, ganglion cyst, and plantar fasciiti s, In addition, a specific diagnosis can almost always be made in pati ents with pigmented villonodular synovitis (PVNS) or giant cell tumor (GCT) of the tendon sheath. The MR imaging appearance of PVNS consists of multiple synovial lesions with low or intermediate signal intensit y on T1-weighted images and low signal intensity on T2-weighted and gr adient-echo images. GCTs of the tendon sheath usually have areas of lo w signal intensity on both T1- and T2-weighted images due to the param agnetic effect of hemosiderin, Awareness and understanding of the unde rlying pathologic findings in lesions of the foot and ankle aid in MR imaging interpretation.