Synovial Sarcoma: A Clinical Review

Abstract

Synovial sarcomas (SS) represent a unique subset of soft tissue sarcomas (STS) and account for 5-10% of all STS. Synovial sarcoma differs from other STS by the relatively young age at diagnosis and clinical presentation. Synovial sarcomas have unique genomic characteristics and are driven by a pathognomonic t(X;18) chromosomal translocation and subsequent formation of the SS18:SSX fusion oncogenes. Similar to other STS, diagnosis can be obtained from a combination of history, physical examination, magnetic resonance imaging, biopsy and subsequent pathology, immunohistochemistry and molecular analysis. Increasing size, age and tumor grade have been demonstrated to be negative predictive factors for both local disease recurrence and metastasis. Wide surgical excision remains the standard of care for definitive treatment with adjuvant radiation utilized for larger and deeper lesions. There remains controversy surrounding the role of chemotherapy in the treatment of SS and there appears to be survival benefit in certain populations. As the understanding of the molecular and immunologic characteristics of SS evolve, several potential systematic therapies have been proposed.

Keywords: clinical review; current concepts; soft tissue sarcoma; synovial sarcoma.

Figure 1

AP (A) and lateral (B) radiographs of the right (R) knee and lower leg in a 31-year-old male demonstrate coarse calcifications within the soft tissues adjacent to the posteromedial tibial plateau, corresponding to a biopsy proven synovial sarcoma. No significant articular abnormality. Adjacent bony structures appear unremarkable.

Figure 2

Sagittal MR images in the same patient demonstrate a periarticular soft tissue mass situated posteromedial to the proximal tibia, in close relation to the pes anserine tendons. The mass demonstrates intermediate signal on T1 weighted images (A), and heterogeneously high signal on T2 weighted fat-saturated images (B). T1 weighted fat-saturated after gadolinium administration (C), demonstrates heterogeneously avid enhancement. Known areas of calcification are low signal on all sequences (arrow).

Figure 3

(A) Microscopic images showing biphasic tumor composed of spindle cell (S) and epithelioid (E) component; H&E ×100 and (B) occasional calcifications (arrow); H&E ×200). (C) Microscopic image showing poorly differentiated morphology (H&E ×400). (D) Immunohistochemistry demonstrating diffuse and strong nuclear staining for the transcriptional corepressor TLE1 (×200).

Figure 4

Molecular study using fluorescence in situ hybridization (FISH) break apart probe confirmed a diagnosis of synovial sarcoma detecting the SS18 gene arrangement (split red and green signal) (×200).