Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Synovial Sarcoma

  • Alessandro FranchiEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_3462-1



Synovial sarcoma (SS) is a malignant mesenchymal tumor showing varying degrees of epithelial differentiation. Despite the designation, it does not originate from synovium, and neoplastic cells do not show evidence of differentiation toward a synovial phenotype.

Clinical Features

  • Incidence

    SS originating in the genitourinary tract is rare.

  • Age

    It occurs in young adults and adults, with median age in the fourth decade.

  • Sex

    There is no significant gender predilection.

  • Site

    Genitourinary SSs arise more frequently in the kidney, but few examples have also been reported in the prostate, the spermatic cord, and the penis.

  • Treatment

    Surgery is the primary treatment, but adjuvant radiotherapy and chemotherapy may also be employed in selected cases.

  • Outcome

    SS is an aggressive tumor with frequent distant metastases and poor survival. In a review of 64 patients with SS of the kidney, the median overall survival was 48 months. Patients with metastatic disease had a very poor survival with a median of 6 months.


SSs are usually large tumors, macroscopically well circumscribed, sometimes with areas of cystic degeneration, as well as with areas of hemorrhage and necrosis.


The majority of urogenital SSs are of the monophasic type, being formed by intersecting fascicles of atypical spindle cells (Fig. 1). A prominent vasculature with “hemangiopericytomatous” features is usually present. Approximately 25% of urogenital SSs present a glandular or solid component formed by epithelioid cells and are therefore classified as biphasic. In rare instances the tumor is poorly differentiated with a significant round cell component.


SS shows limited positivity for epithelial markers, including cytokeratins and EMA. Nuclear positivity for TLE1 is present in almost all cases. Other positive markers include bcl2 and CD99, while CD34, smooth muscle actin, and desmin are negative.

Molecular Features

SS presents a translocation t(X;18)(p11;q11) that results in the fusion of SS18 gene with either SSX1 or SSX2 genes.

Differential Diagnosis

The main differential diagnosis of urogenital SS is with sarcomatoid carcinoma. Both tumor types may show partial cytokeratin positivity, but sarcomatoid carcinoma is negative for TLE1 and does not show the SS18-SSX fusion. Mesenchymal tumors that can be considered in the differential diagnosis include solitary fibrous tumor, which is positive for CD34 and STAT6, and malignant peripheral nerve sheath tumor, which does not present the SS18-SSX rearrangement. Poorly differentiated SS needs to be distinguished from Ewing sarcoma.
Fig. 1

Monophasic synovial sarcoma showing a fasciculated pattern of spindle cells

References and Further Reading

  1. Argani, P., Faria, P. A., Epstein, J. I., Reuter, V. E., Perlman, E. J., Beckwith, J. B., & Ladanyi, M. (2000). Primary renal synovial sarcoma: Molecular and morphologic delineation of an entity previously included among embryonal sarcomas of the kidney. The American Journal of Surgical Pathology, 24, 1087–1096.CrossRefGoogle Scholar
  2. Iacovelli, R., Altavilla, A., Ciardi, A., Urbano, F., Manai, C., Gentile, V., & Cortesi, E. (2012). Clinical and pathological features of primary renal synovial sarcoma: Analysis of 64 cases from 11 years of medical literature. BJU International, 110, 1449–1454.CrossRefGoogle Scholar
  3. Olofson, A. M., & Linos, K. (2017). Primary intraprostatic synovial sarcoma. Archives of Pathology & Laboratory Medicine, 141, 301–304.CrossRefGoogle Scholar
  4. Sasso, F., Delicato, G., Gentile, G., Falabella, R., & Gentile, V. (2002). Primary synovial sarcoma of the penis. The Journal of Urology, 168(2), 633. Erratum in: J Urol. 2003;169:622.CrossRefGoogle Scholar
  5. Schoolmeester, J. K., Cheville, J. C., & Folpe, A. L. (2014). Synovial sarcoma of the kidney: A clinicopathologic, immunohistochemical, and molecular genetic study of 16 cases. The American Journal of Surgical Pathology, 38, 60–65.CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Translational Research and of New Technologies in Medicine and SurgeryUniversity of PisaPisaItaly