MR and CT appearance of nodular fasciitis

Nodular fasciitis is a common soft-tissue tumor that remains almost unreported in the radiology literature. We retrospectively reviewed all available imaging studies on three patients with nodular fasciitis studied by MR at our institution. The lesions were round to oval in configuration, ranging in size from 1 to 4.5 cm. Two were intramuscular and one was subcutaneous in location. Both intramuscular lesions were poorly defined on CT, with a tissue attenuation less than that of skeletal muscle. The single subcutaneous lesion was well defined by surrounding fat. Conversely, all lesions were well defined on MR, although the appearance was otherwise nonspecific and varied according to the histology of the lesion. Both intramuscular lesions were mucoid or cellular and were hyperintense to skeletal muscle on T1-weighted and hyper-intense to fat on T2-weighted spin-echo (SE) MR images. The subcutaneous lesion was fibrous and markedly hypointense to skeletal muscle on all SE pulse sequences. Findings on three-phase bone scan, arteriography, and ultrasound are discussed. Because there are no unique radiologic findings in nodular fasciitis, this entity must be included in the preoperative differential diagnosis of small soft-tissue masses occurring in the extremities of young adults.