Synovial sarcoma

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Synovial sarcoma, abbreviated SS, is an uncommon malignant soft tissue tumour, typically seen in young adults.

Synovial sarcoma
Diagnosis in short

Monophasic synovial sarcoma. H&E stain.
LM one of the following: (1) spindle cell sarcoma with features of hemangiopericytoma, i.e. staghorn vessels; (2) biphasic synovial sarcoma (spindle cells with features of hemangiopericytoma, epitheliod glands or nests); (3) primitive round cell type
LM DDx MPNST, hemangiopericytoma, fibrosarcoma, small round cell tumours, carcinoma
IHC Vimentin +ve, EMA +ve, BCL2 +ve, CD99 +ve.
Molecular t(X;18)
Gross usually lower extremity, usually close to a joint
Site soft tissue
Clinical history young adults or adolescents
Signs mass +/-pain
Prevalence uncommon
Prognosis poor

General

  • Does not arise from cartilage.[1]
  • Young adults or adolescents.
    • Classic age: 30s.
  • Poor prognosis.

Clinical:[2]

  • Present with soft palpable mass - slow growing - often for years.
  • May present with pain.
    • Uncommon finding in sarcomas.

Gross

Location:

  • Usually close to a joint.
  • Usually distal extremity ~65% of cases.[2]
    • Upper extremity ~20% of cases.[2]

Appearance - often non-specific:

  • Solid often lobulated +/- cystic component.
  • Grey-yellow.
  • Pushing border to ill-defined border.

Images:

Microscopic

Comes in three (histologic) flavours:[1][4]

  1. Spindle cell sarcoma with features of hemangiopericytoma, i.e. staghorn vessels.
  2. Biphasic synovial sarcoma:
    1. Spindle cells with features of hemangiopericytoma.
    2. Epitheliod glands or nests.
  3. Primitive round cell type.

Features:

  • Herring bone or vesicular pattern - key feature.
  • Spindle cells.
  • +/-Glandular component - typically more pink.
  • +/-Calcification - uncommon.
    • Extensive calcification = better prognosis.[5]

DDx:

Images

  • Monophasic synovial sarcoma with staghorn vessels - intermed. mag. (WC/Nephron)

  • Monophasic synovial sarcoma with staghorn vessels - high mag. (WC/Nephron)

www:

IHC

Features:[1]

  • Vimentin +ve.
  • EMA +ve.
  • BCL2 +ve.
  • CD99 +ve.

Others:

  • Beta-catenin +ve ~30-70%.[6]
  • Cyclin D1 ~50%.[6][7]
  • TLE1 +ve nuclear staining; not specific for synovial sarcoma.[8][9]

Typically negative:[10]

  • CD34.
  • S100 ~30% +ve.
  • SMA.

Notes:

  • Synovial sarcoma & MPNST:
    • Both +ve: PGP9.5 (UCHL1[11]), S100, NGFR, CD56, CD99, vimentin.
    • Synovial +ve: EMA, keratin, BCL2, TLE1.
    • MPNST +ve: nestin, CD34.

Trivia:

  • PGP in PGP9.5 = protein gene product.[12]

EM

Features:[13]

  • Biphasic tumour have biphasic ultrastructural features (unlike spindle cell carcinoma and epithelioid sarcoma).
  • Epithelioid component is adenocarcinoma-like - they have:
  • Spindle cell component - mostly features less.
    • Poorly formed desmosomes.
    • No intermediate filaments, no myofilaments.

Molecular pathology

Associated translocation:

  • t(X;18)(p11.2;q11.2).[14]
    • SYT/SSX fusion gene.

Several SSX genes - cannot be differentiated with standard karyotyping:

  • SSX1.
  • SSX2 - better survival, rarely seen in biphasic tumours.[15]
  • SSX4 - uncommon.

Notes:

  • At HSC t(X,18) = synovial sarcoma.

See also

References

  1. ↑ 1.0 1.1 1.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 627. ISBN 978-0781765275.
  2. ↑ 2.0 2.1 2.2 Murphey, MD.; Gibson, MS.; Jennings, BT.; Crespo-Rodríguez, AM.; Fanburg-Smith, J.; Gajewski, DA.. "From the archives of the AFIP: Imaging of synovial sarcoma with radiologic-pathologic correlation.". Radiographics 26 (5): 1543-65. doi:10.1148/rg.265065084. PMID 16973781.
  3. ↑ URL: http://www.sarcomaimages.com/index.php?v=Synovial-Sarcoma. Accessed on: 2 April 2012.
  4. ↑ Schaal CH, Navarro FC, Moraes Neto FA (2004). "Primary renal sarcoma with morphologic and immunohistochemical aspects compatible with synovial sarcoma". Int Braz J Urol 30 (3): 210–3. PMID 15689250. http://www.brazjurol.com.br/may_june_2004/Schaal_ing_210_213.htm.
  5. ↑ Varela-Duran, J.; Enzinger, FM. (Jul 1982). "Calcifying synovial sarcoma.". Cancer 50 (2): 345-52. PMID 6282441.
  6. ↑ 6.0 6.1 Horvai AE, Kramer MJ, O'Donnell R (June 2006). "Beta-catenin nuclear expression correlates with cyclin D1 expression in primary and metastatic synovial sarcoma: a tissue microarray study". Arch. Pathol. Lab. Med. 130 (6): 792–8. PMID 16740029.
  7. ↑ Ng TL, Gown AM, Barry TS, et al. (January 2005). "Nuclear beta-catenin in mesenchymal tumors". Mod. Pathol. 18 (1): 68–74. doi:10.1038/modpathol.3800272. PMID 15375433.
  8. ↑ Kosemehmetoglu K, Vrana JA, Folpe AL (July 2009). "TLE1 expression is not specific for synovial sarcoma: a whole section study of 163 soft tissue and bone neoplasms". Mod. Pathol. 22 (7): 872–8. doi:10.1038/modpathol.2009.47. PMID 19363472. http://www.nature.com/modpathol/journal/v22/n7/full/modpathol200947a.html.
  9. ↑ Seo SW, Lee H, Lee HI, Kim HS (February 2011). "The role of TLE1 in synovial sarcoma". J Orthop Res. doi:10.1002/jor.21318. PMID 21319215.
  10. ↑ URL: http://path.upmc.edu/cases/case292/dx.html. Accessed on: 14 January 2012.
  11. ↑ Online 'Mendelian Inheritance in Man' (OMIM) 191342
  12. ↑ Doran, JF.; Jackson, P.; Kynoch, PA.; Thompson, RJ. (Jun 1983). "Isolation of PGP 9.5, a new human neurone-specific protein detected by high-resolution two-dimensional electrophoresis.". J Neurochem 40 (6): 1542-7. PMID 6343558.
  13. ↑ Fisher, C. (Dec 1998). "Synovial sarcoma.". Ann Diagn Pathol 2 (6): 401-21. PMID 9930576.
  14. ↑ URL: http://www.ncbi.nlm.nih.gov/omim/300813. Accessed on: 30 May 2010.
  15. ↑ Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 625 Q6. ISBN 978-1416025887.
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