Cyst-like solid tumors of the musculoskeletal system: an analysis of ultrasound findings

When evaluating superficial soft tissue masses with ultrasonography, it is not always clear whether the mass is cystic or solid. We reviewed sonograms of soft tissue masses, which were interpreted as cystic but confirmed as solid tumors. We scanned a database of patients with superficial soft tissue masses from two different institutions. Four hundred and thirty lesions were evaluated with ultrasonography and then confirmed surgically. Twenty-three masses were identified, of which initial interpretation on gray scale included cystic tumor which pathology revealed to be solid tumors. All images were evaluated by two musculoskeletal radiologists, regarding internal echogenicity of lesions, presence of posterior enhancement, margins, size, and internal vascularity. Of 23 masses, there were 5 giant cell tumors of the tendon sheath, 4 schwannomas, 3 vascular leiomyomas, 2 benign fibrous histiocytomas, 2 dermatofibrosarcoma protuberans, 2 granular cell tumors, 1 dermatofibroma, 1 fibroma of the tendon sheath, 1 fibromatosis, 1 eccrine spiradenoma, and 1 granulation tissue. Masses were hypoechoic in 16 and anechoic in 7 cases. Posterior enhancement was present in 9, and 10 masses showed no internal vascularity on color Doppler imaging. Margins were smooth in 13, smooth with mild lobulation in 7, and lobulated in 3 cases. Mean size was 2.3 cm. On ultrasonography, solid soft tissue tumors may be confused with cystic masses. Such cases are not common, and fibrous tumors are the most frequent. Care should be given to these solid tumors that have a cystic appearance and even lack internal vascularity on color Doppler imaging to enhance diagnosis of cystic and solid masses.