Background: Synovial sarcoma of the kidney is rare. It is clinicoradiologically indistinguishable from the more frequently encountered renal cell carcinoma. Histologically it needs to be differentiated from other spindle cell lesions occurring within the kidney, including a spectrum of benign to malignant tumors. Among malignant spindle cell tumors of the kidney, mimics of synovial sarcoma are sarcomatoid renal cell carcinoma, sarcomatoid urothelial carcinoma and other primary sarcomas, such as leiomyosarcoma and malignant fibrous histiocytoma.
Cases: Four cases of synovial sarcoma originated in the kidney, with this report focusing on clinicopathologic and differential diagnostic features.
Conclusion: The correct diagnosis of synovial sarcoma requires support by an immunohistochemical panel as well as adjunctive investigations like polymerase chain reaction and fluorescence in situ hybridization to determine the presence of the SYT-SSX fusion gene and translocation (X,18), respectively.