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.
SS originating in the genitourinary tract is rare.
It occurs in young adults and adults, with median age in the fourth decade.
There is no significant gender predilection.
Genitourinary SSs arise more frequently in the kidney, but few examples have also been reported in the prostate, the spermatic cord, and the penis.
Surgery is the primary treatment, but adjuvant radiotherapy and chemotherapy may also be employed in selected cases.
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.
SS presents a translocation t(X;18)(p11;q11) that results in the fusion of SS18 gene with either SSX1 or SSX2 genes.
References and Further Reading
- 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