Sonographic appearance of nodular fasciitis

First described in 1955, nodular fasciitis, or pseudosarcomatous fibromatosis, is a benign, self-limiting reactive process composed of proliferating fibroblasts in a myxoid stroma. A rich cellular array of spindle-shaped fibroblasts, microhemorrhages, and numerous mitotic figures are characteristic features on low-magnification light microscopy. Nodular fasciitis most commonly appears in the third and fourth decades with a solitary, rapidly growing, sometimes painful nodule arising in the upper extremity, which can be clinically confused with a sarcoma. Although a relatively common lesion, nodular fasciitis is underreported in the radiology literature. Typical magnetic resonance imaging (MRI) findings include low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, although they vary in homogeneity and patterns of enhancement. On sonography, nodular fasciitis has been described as oval or lobulated, isoechoic, or with mixed areas of isoechogenicity and hypoechogenicity. As described below, we report a case of a patient with nodular fasciitis who underwent extensive imaging including sonography and MRI and describe the imaging features of this disease process. In this case, the lesion was well defined and slightly hypoechoic yet mildly heterogeneous and showed posterior acoustic enhancement.