Clinical and pathological features of primary renal synovial sarcoma: analysis of 64 cases from 11 years of medical literature

Objective: To describe, for the first time, the clinical characteristics of primary renal synovial sarcoma (SS) and to examine the association of histological features with the expression of immunohistochemical markers.

Patients and methods: We collated published data on all cases of primary renal SS, from its first description in 2000 to September 2011. Data on clinical and pathological characteristics were extracted and used to create a database. Disease-free survival (DFS) and overall survival (OS) rates were estimated using the Kaplan-Meier method with Rothman's 95% confidence intervals (CIs) and compared across the groups using the log-rank test. The associations between tumour extension and histological features were evaluated using the non-parametric Spearman rank test. A chi-squared test was used to assess the differences between groups.

Results: In the overall cohort, the median OS was 48 months (95% CI, 14.1-81.9). Cox analysis showed that the risk of death at diagnosis was greatly increased in patients with metastatic disease compared with those with non-metastatic disease (hazard ratio [HR]: 343.9, 95% CI, 2.8-42,000; P= 0.017). The median DFS was 33.0 months (95% CI, 16.8-49.2), and patients who develop metastatic disease have a very poor prognosis with a median survival of 6 months (95% CI, 5.1-6.9). Microscopic features were monophasic, biphasic and poorly differentiated synovial sarcoma in 76, 16 and 8% of patients, respectively. Significant differences in expression of immunohistochemical markers or genetic mutation were found between different subtypes.

Conclusions: Despite its retrospective nature, this study shows that renal SS comprises different histological subtypes, which are characterized by specific immunohistochemical stains and by specific translocations. When diagnosed at metastatic stage, the prognosis was very poor compared with that for non-metastatic disease, even though one out of three patients with non-metastatic disease had disease relapse. Cooperative efforts and publication of cases with adequate follow-up are necessary to better define prognosis and therapeutic strategies for this rare disease.