Plantar fibromatosis: most common sonographic appearance and variations

The aim of this study was to describe the most common sonographic appearances of plantar fibromatosis, thus enabling sonographic diagnosis of this benign, focally invasive fibrous neoplasm.

The medical records, pathologic reports, and sonographic reports and images of 22 patients with palpable plantar masses were reviewed retrospectively. The sonographic findings were used to characterize those masses with respect to location, shape, size, and echogenicity. Sixteen patients were included in this study because of the proximity of their lesions to the plantar fascia; 6 patients were excluded because their lesions were metatarsophalangeal bursae or ganglia.

The 20 feet examined in the 16 patients studied contained 43 distinct lesions, all located on the surface of the plantar fascia. Thirty-seven (86%) of the 43 were 20 mm long or less. Thirty-seven (86%) of the 43 lesions were elongated; the remaining 6 (14%) were round or oval. Twenty-five (68%) of the 37 elongated lesions had tapered ends, and the other 12 (32%) had rounded ends. Thirty-one (72%) of the 43 lesions were hypoechoic; 25 (81%) of these 31 measured as long as 10 mm. Ten (83%) of the 12 lesions that had mixed echogenicity were longer than 10 mm.

The lesions of plantar fibromatosis were characteristically located on the surface of the plantar fascia, sagittally elongated, most often less than 20 mm long, fusiform, and hypoechoic. Lesions longer than 10 mm often exhibited mixed echogenicity. The superficial location and appearance should strongly suggest plantar fibromatosis, although careful examination is required to exclude other possibilities, such as sarcoma.