Extensively Calcified Synovial Sarcoma

Synovial cell sarcomas, discussed earlier, can present with calcifications in about 30% of cases. The calcifications are often diffuse and punctate. Extensive calcification simulating a cartilaginous or bony tumor is uncommon, but has been reported to have a better prognosis, with higher survival rates.

The image above shows such a case. The radiograph of the shoulder shows an extensively calcified lesion adjacent to the scapula. A discontinuity in the pattern of calcification superiorly is better appreciated on CT as a soft tissue component anteriorly that is metabolically active on the PET/CT fused image. MRI shows hypointensities corresponding to the calcification posteriorly, as well as a T1-hypointense, T2-hyperintense, enhancing soft tissue component anteriorly.

The radiographic differential diagnosis includes soft tissue chondroma, extra-articular synovial chondromatosis, ossifying myositis, tumoral calcinosis, and even extraskeletal osteosarcoma.

The CT suggests a more aggressive process due to the presence of the soft tissue component, which is confirmed on PET and MRI imaging.

Cases of ossifying synovial sarcomas have also been described, containing not simply calcification, but ossified matrix.

References

• Hisaoka M, Matsuyama A, Shimajiri S, Akiba J, Kusano H, Hiraoka K, Shoda T, Hashimoto H. Ossifying synovial sarcoma. Pathol Res Pract. 2009;205(3):195-8.
• Maxwell JR, Yao L, Eckardt JJ, Doberneck SA. Case report 878: Densely calcifying synovial sarcoma of the hip metastatic to the lungs. Skeletal Radiol. 1994 Nov;23(8):673-5.
• Sánchez Reyes JM, Alcaraz Mexia M, Quiñones Tapia D, Aramburu JA. Extensively calcified synovial sarcoma. Skeletal Radiol. 1997 Nov;26(11):671-3.
• Winnepenninckx V, De Vos R, Debiec-Rychter M, Samson I, Brys P, Hagemeijer A, Sciot R. Calcifying/ossifying synovial sarcoma shows t(X;18) with SSX2 involvement and mitochondrial calcifications. Histopathology. 2001 Feb;38(2):141-5.