Primary renal synovial sarcomas (SS) are rare tumors of the kidney. Faria et al first described primary renal synovial sarcoma in 1999 (Mod Pathol 12:94A). In this paper we present a primary renal synovial sarcoma case and review the 41 primary renal synovial sarcoma cases reported to date. Primary renal synovial sarcomas can exist in either a monophasic or a biphasic pattern. The monophasic variant of primary renal synovial sarcoma is more common and tends to have a better prognosis than the biphasic variant. We present in this paper, a 68-year-old woman with primary renal synovial sarcoma. She presented with right flank pain and abdominal distention. Postoperative pathology of the 20 cm mass on magnetic resonance imaging showed histologic and immunochemical features of synovial sarcoma with coexisting spindle and epithelial cells. She underwent adjuvant ifosfamide and doxorubicin chemotherapy and was free of disease at 1 year after diagnosis. As a conclusion, physicians should be aware of the possibility of malignancy in cystic renal masses and that synovial sarcoma is one of the possibilities.