Synovial Sarcoma Mimicking Myositis Ossificans

Abstract

A calcification mass was incidentally found in the soft tissue of a patient who had a history of trauma to the extremity during examination. The patient had no symptom. The pathological analysis of the mass revealed it was an early-phase synovial sarcoma (SS). The diagnosis was made before the onset of symptoms and proper surgical intervention was performed. Therefore, in case of a <1 cm lesion clinically suspicious of myositis ossificans, SS should be taken into consideration as a possible diagnosis.

Keywords: Femur; Injury; Myositis ossificans; Neoplasm; Soft tissue; Synovial sarcoma.

Fig. 1. Radiograph showing a radiopaque mass measuring 10 mm in diameter on the lateral side of left femur. a: radiopaque mass (white arrow), b: ring-shaped wire (white arrow).

Fig. 2. (A) Spindle tumor cells containing common dystrophic calcification (black arrows) (H&E, ×100). The tumor cells were focal positive for cytokeratin 7 (B) and diffuse positive for vimentin (C) with a low Ki-67 proliferation index (D) (Immunostaining, ×200).

Fig. 3. (A) Sagittal magnetic resonance imaging scan showing a mass on the lateral side of the left thigh (white arrow). (B) Anteroposterior radiograph showing a radiopaque mass (white arrow).