Soft-tissue tumors of the foot: value of MR imaging for specific diagnosis.

We reviewed MR imaging findings in 14 patients with primary soft-tissue tumors of the foot and compared them with surgical and pathologic findings to determine the value of MR imaging in anatomic localization, delineation, and characterization of such lesions. Nine tumors (64%) were benign, and five (36%) were malignant. The anatomic location (compartment, space, relation to specific tendon) and extent of all tumors were accurately shown by MR imaging. Twelve tumors (86%) were correctly characterized as benign or malignant. Eight (89%) of nine benign lesions showed distinctive MR imaging features that correctly suggested a specific diagnosis. These included hemangioma (high T2-weighted intensity and internal septa), ganglion cyst (homogeneous, high T2-weighted weighted intensity and peritendinous location), plantar fibromatosis (nodularity of plantar aponeurosis with low intensity on all sequences), and pigmented villonodular synovitis (low T2-weighted intensity and lower intensity rim). Aggressive fibromatosis (one case) could not be characterized. Four (80%) of five malignant neoplasms had MR imaging findings suggesting soft-tissue sarcoma. Two synovial sarcomas were inhomogeneous and showed extensive peritendinous growth. Two clear cell sarcomas arose at the origin of the plantar aponeurosis and infiltrated adjacent muscle. A small clear cell sarcoma could not be characterized as benign or malignant. MR imaging of the foot is accurate in showing the extent of soft-tissue tumors, which is helpful for surgical planning. Determination of their specific anatomic location may help characterize some tumors. Although our series is small, it appears that MR imaging often suggests a specific diagnosis in certain benign soft-tissue tumors of the foot and may often correctly distinguish benign from malignant tumors.