synovial sarcoma

Digital cases

 JRC:6541 : Synovial sarcoma of soft tissues.

Definition: Human synovial sarcomas are aggressive soft tissue tumors with relatively high rates of recurrences and metastases. They display a variable response to common treatment protocols such as radiation and chemotherapy.

Localization

 soft tissue
 nerve (intraneural synovial sarcoma) (#14685256#)
 kidney (renal synovial sarcoma)
 liver (hepatic synovial sarcoma) (#16048399#)

Variants

 monophasic synovial sarcoma
 with rhabdoid tumoral cells (#14521444#, #15105652#)
 poorly differentiated synovial sarcoma

Immunochemistry

 Beta-catenin+ (#16740029#, #15375433#, #11213832#, #10189891#)

• The synovial sarcoma translocation protein SYT-SSX2 recruits beta-catenin to the nucleus and associates with it in an active complex. (#16462762#)
• Aberrant beta-catenin expression has prognostic relevance. (#16740029#, #11274633#, #11054718#)
• +/- Association between aberrant (nuclear) beta-catenin expression and cyclin D1 accumulation (#16740029#, #16733209#)

Differential diagnosis

 fusiform cell tumors

• fibrosarcomas
  • adult-type fibrosarcoma

Molecular biology

Synovial sarcoma is characterized cytogenetically by the t(X;18)(p11;q11) translocation, resulting in fusion between the SS18 gene on chromosome 18 and one of the SSX genes on the X chromosome.

 SS18/SSX1
 SS18/SSX2
 SS18/SSX4

These three fusion genes account for more than 95% of the synovial sarcomas.

 SS18L1/SSX1 (#12696068#)

The SS18 and SSX genes encode nuclear proteins that exhibit opposite transcription regulatory activities, likely through epigenetic mechanisms. The SS18 protein functions as a transcriptional coactivator and interacts directly with members of the epigenetic chromatin remodeling and modification machineries.

In contrast, the SSX proteins function as transcriptional corepressors and are associated with several Polycomb group proteins. Since the domains involved in these apparently opposite transcription regulatory activities are retained in the SS18-SSX fusion proteins, these fusion proteins can function as "activator-repressors" of transcription.

Case records

 Case 11736: Axilary synovial sarcoma
 pathxchange.org #15007

See also

 Tumors

• Sarcomas
• fusiform cell tumors
• biphasic tumors
• synovial tumors

References

 Gene expression profiling of synovial sarcoma: distinct signature of poorly differentiated type. Nakayama R, Mitani S, Nakagawa T, Hasegawa T, Kawai A, Morioka H, Yabe H, Toyama Y, Ogose A, Toguchida J, Nakayama T, Yoshida T, Ichikawa H. Am J Surg Pathol. 2010 Nov;34(11):1599-607. PMID: #20975339#

 Prospective Evaluation of TLE1 as a Diagnostic Immunohistochemical Marker in Synovial Sarcoma. Jagdis A, Rubin BP, Tubbs RR, Pacheco M, Nielsen TO. Am J Surg Pathol. 2009 Oct 3. PMID: #19809272#

 de Bruijn DR, Nap JP, van Kessel AG. The (Epi)genetics of human synovial sarcoma. Genes Chromosomes Cancer. 2007 Feb;46(2):107-17. PMID: #17117414#

 Kanemitsu S, Hisaoka M, Shimajiri S, Matsuyama A, Hashimoto H. Molecular detection of SS18-SSX fusion gene transcripts by cRNA in situ hybridization in synovial sarcoma using formalin-fixed, paraffin-embedded tumor tissue specimens. Diagn Mol Pathol. 2007 Mar;16(1):9-17. PMID: #17471153#