Object:

To evaluate MRI findings of primary synovial sarcoma and to differentiate recurrent tumor from post-treatment changes.

Material and methods:

We retrospectively analyzed pre and post-treatment MRI findings of proven primary and recurrent synovial sarcomas in 22 patients. MRI findings were correlated with histological diagnoses and clinical follow-ups for 1-5 years.

Results:

Ninety-one percent of the studied synovial sarcomas were in the extremities (68 percent) in the lower extremities), and sizes ranged 3-12 cm. Aproximately 73 percent of the primary tumors were located less than 5 cm. from a synovial joint. Most common MRI findings were nodular masses with heterogeneous intermediate signal intensity (SI) on T1 weighted images (WI), high SI on T2-WI and heterogenous contrast enhancement. A cystic component was recognized in 17 cases (77 percent). Ninety percent of the sarcomas were oval and well-defined. MRI findings consistent with intratumoral hemorrhage was noted in 73 percent. Lung and nodal metastases were found in 27 percent and 5 percent respectively. Lung metastases were found more commonly in biphasic than monophasic histologic types (50 percent vs 41 percent). Involvement of adjacent bones was seen in 23 percent (3 biphasic abc 2 monophasic sarcomas). Calcification was only noted in three monophasic sarcomas on plain films and CT. Two recurrent sarcomas showed focal nodular masses with high SI on T2-WI and homogenous contrast enhancement. Post-treatment changes revealed diffusely increased SI on T2-WI and slight diffuse contrast enhancement with feathery appearence.

Conclusion:

Detection of primary and recurrent synovial sarcoma can be made by recognizing both morphology and MR signal characteristics including contrast enhancement pattern. Contrary to other reports, sarcomas with biphasic histologic type showed more metastases and bone involvement. Association between calcifications and monophasic type was not previously reported