The role of magnetic resonance imaging in the evaluation of the soft tissue mass.

Magnetic resonance imaging is used widely to investigate soft tissue masses. The effectiveness of MRI derives from unrivaled soft tissue contrast and multiplanar imaging capability. Magnetic resonance spectroscopy has been used to examine the phosphometabolites of normal and pathological soft tissues. We review the role of MRI and MRS in the detection and characterization of soft tissue masses and in staging soft tissue malignancies. The detection of a soft tissue mass depends on image contrast between normal and pathological tissue. We review the salient factors, both intrinsic properties of tissues and parameters of MR imaging, which influence soft tissue contrast on an MR image. Specific pulse sequences that have been compared for tumor detection are discussed. One goal of a radiological test is to provide tissue-specific characterization. Alone or in combination, various MR imaging characteristics of a soft tissue mass have been studied for an association with benign or malignant tissue. MR imaging signs discussed in this review include signal intensity, relaxation time, homogeneity of signal pattern, septation, size at presentation, shape, margin definition, peritumoral edema, involvement of bone or neurovascular tissue, and contrast enhancement. The MR imaging appearance of hemangioma, lipoma, pigmented villonodular synovitis, desmoid tumor, hematoma, arteriovenous malformation, and ganglion cyst is also reviewed. MR imaging is the quintessential imaging method for staging a soft tissue malignancy. We review three staging systems in common use and the role of MR imaging for local staging of untreated and treated soft tissue malignancies.