2021-22/ May 31
Contributors: Bindu Challa and Anil Parwani

A man in his 70s presented with right flank pain. Computed Tomography (CT) Abdomen and Pelvis showed a large right renal mass with direct invasion of the right hepatic lobe and a likely tumor thrombus in the right renal vein. He underwent right radical nephrectomy with regional lymphadenectomy.


1. What is the correct diagnosis?

a. Wilms tumor

b. Leiomyosarcoma

c. Primary renal Ewing sarcoma

d. Sarcomatoid renal cell carcinoma

e. Primary renal synovial sarcoma

1. Primary renal synovial sarcoma

Primary renal synovial sarcoma is the rarest type of renal sarcoma, constituting less than 1% of all renal tumors. About 50 cases have been reported in literature thus far. It affects young people between 20 and 50 years of age and has no gender predilection. On imaging, primary renal synovial sarcoma is typically solid or cystic, with heterogeneous enhancement, hemorrhage, and necrosis seen within the tumor, as well as calcification and hypovascularity.

Histologically, primary renal synovial sarcoma is classified into biphasic, monophasic, spindle cell and poorly differentiated types. The poorly-differentiated variants represent 20% of cases, have the poorest prognosis, and may be categorized into three histologic subvariants: large cell, small cell and high-grade spindle cell variants. The monophasic type can look like fibrosarcoma, leiomyosarcoma, malignant peripheral nerve sheath tumors, adult Wilms tumor, spindle cell carcinoma, and spindle cell melanoma. While monophasic synovial sarcoma of the kidney is composed exclusively of monomorphic spindle cells, the biphasic type is a mixture of both spindle-shaped cells and epithelial cells.

By immunohistochemistry, TLE1 (nuclear stain) is a sensitive and specific for synovial sarcoma. CD56, Bcl2, CD99, and EMA (focal) can also be positive. The tumor is negative for CD34, S-100, CD31, desmin, and actin immunostains. Molecular testing for the chromosomal translocation t(X;18) (p11.2;q11.2) that causes fusion of SYT gene on chromosome 18 with SSX family gene on chromosome X helps to confirm the diagnosis. Treatment includes radical surgical resection.

1. El Chediak A, Mukherji D, Temraz S, Nassif S, Sinno S, Mahfouz R, Shamseddine A. Primary synovial sarcoma of the kidney: a case report of complete pathological response at a Lebanese tertiary care center. BMC Urol. 2018 May 11;18(1):40.

2. Gaurang Modi, Irappa Madabhavi, Harsha Panchal, Asha Anand, Apurva Patel, Sonia Parikh, Swaroop Revannasiddaiah, “Primary Synovial Sarcoma of Kidney: A Rare Differential Diagnosis of Renomegaly”, Case Reports in Pathology, vol. 2014.

3. Kawahara T, Sekiguchi Z, Makiyama K, Nakayama T, Nagashima Y, Kita K, Namura K, Itou H, Sano F, Hayashi N, Nakaigawa N, Ogawa T, Uemura H, Yao M, Kubota Y. Primary Synovial Sarcoma of the Kidney. Case Rep Oncol. 2009 Oct 14;2(3):189-193.

4. Cai HJ, Cao N, Wang W, Kong FL, Sun XX, Huang B. Primary renal synovial sarcoma: A case report. World J Clin Cases. 2019 Oct 6;7(19):3098-3103.

Bindu Challa
Anil Parwani
Ohio State University Wexner Medical Center
Columbus, Ohio


kidney, spindle cells, synovial sarcoma, SS18(SYT) gene, TLE1