Synovial Sarcoma



Synovial Sarcoma


Cyril Fisher, MD, DSc, FRCPath









Hematoxylin & eosin shows a biphasic synovial sarcoma (SS) with irregular-shaped glandular structures image dispersed in a spindle cell component. The epithelial cell nuclei are rounded and uniform.






Hematoxylin & eosin shows monophasic SS composed of irregular small short or ovoid spindle cells with apparently overlapping vesicular nuclei. Note the absence of nuclear pleomorphism.


TERMINOLOGY


Abbreviations



  • Synovial sarcoma (SS)


Synonyms



  • Terms no longer commonly used



    • Synovial cell sarcoma


    • Malignant synovioma


Definitions



  • Mesenchymal spindle cell tumor with variable epithelial differentiation, including gland formation



    • Characterized by specific chromosomal translocation t(X;18)(p11;q11)


  • Name is historical accident



    • Tumor does not arise from or differentiate toward synovium


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Very rare examples arise in field of prior irradiation


  • 1 case reported at site of metal prosthetic implant


Acquired Genetic Abnormality



  • Translocation between chromosomes × and 18


CLINICAL ISSUES


Epidemiology



  • Incidence



    • 5-10% of all soft tissue sarcomas


    • Can occur in any anatomic location; rare in joints


    • 90% in extremities



      • Most common around knee region


      • In periarticular soft tissue and tendon sheaths


    • Subset in head and neck



      • Parapharynx, oral cavity, tonsil


    • Rare subsets



      • Abdominal wall


      • Retroperitoneum/omentum


      • Mediastinum


      • Intravascular, intraneural


  • Age



    • Majority in young adults 15-35 years


    • Rare over age of 50


  • Gender



    • More frequent in males


Presentation



  • Slow growing


  • Deep mass, with local pressure effects


  • Painful mass



    • > 1/2 of cases


  • Painless mass



    • < 1/2 of cases


Natural History



  • Can be present for long period: 2-20 years


  • Local recurrence frequent especially if inadequate resection


  • Metastasis in 45% of cases



    • Lung (95%)



      • Late metastases can appear after many years


    • Bone


    • Lymph nodes (10%)


Treatment



  • Options, risks, complications



    • Based on



      • Size, location of primary tumor, and stage


  • Adjuvant therapy



    • Preoperative irradiation for large or initially unresectable primary tumor


    • Chemotherapy for disseminated disease



      • Ifosfamide or doxorubicin


      • Combination chemotherapy


  • Surgical approaches



    • Local excision of primary tumor with clear margin




      • Limb sparing


      • Amputation rarely required


    • Excision of recurrences



      • Limb sparing where possible


      • Radical, including amputation


    • Pulmonary metastasectomy for small numbers of metastases


Prognosis



  • 5-year survival (50-85%)


  • Presence of biphasic pattern does not influence behavior


  • Favorable prognostic factors



    • Small tumor size (< 5 cm)


    • Young age, especially childhood


    • Calcifying/ossifying variant (not in all series)


    • Possibly tumors with SSX2 gene rearrangement (not in all series)


  • Adverse prognostic factors



    • Age > 40 years


    • Large tumor size (> 5 cm)


    • Poorly differentiated histology


IMAGE FINDINGS


General Features



  • Best diagnostic clue



    • Scattered calcifications


    • Circumscribed mass


  • Location



    • 1st consideration for tumors around knee


  • Size



    • Variable



      • Usually > 5 cm in diameter


      • Can be very small


      • Rarely > 10 cm, though up to 15 cm described


  • Morphology



    • Circumscribed


Specimen Radiographic Findings



  • Small scattered calcifications


MACROSCOPIC FEATURES


General Features



  • Circumscribed tan tumor mass


  • Soft cut surface


  • Cysts occasionally seen



    • Smooth walled


    • Contain mucoid fluid or blood


  • Focal necrosis and hemorrhage in poorly differentiated tumors


Sections to Be Submitted



  • Sample margins and representative sections of tumor


Size



  • Wide range from minute (< 1 cm) to 15 cm diameter


MICROSCOPIC PATHOLOGY


Histologic Features



  • Sheets of uniform small spindle cells with ovoid nuclei and scanty cytoplasm


  • Focal epithelial differentiation



    • Glandular structures


    • Solid cords or nests


  • Intercellular stroma minimal except in



    • Occasional hyalinizing monophasic SS


    • Calcifying variants


    • Recurrences after irradiation


Lymphatic/Vascular Invasion



  • Rarely


Margins



  • Infiltrative microscopically, pseudocapsule of adjacent tissue


Lymph Nodes



  • Metastases in up to 10% of cases


Predominant Pattern/Injury Type



  • Fascicular



    • Herringbone



    • Sheets


    • Ill-defined palisading occasionally seen


    • Hemangiopericytic pattern common, especially in poorly differentiated SS


Predominant Cell/Compartment Type



  • Spindle and epithelioid


  • Small round


Grade



  • Either grade II or III; never grade I


ANCILLARY TESTS


Cytology



  • Diagnosis can be made on cell-rich aspirates



    • Biphasic pattern rarely seen


    • Monophasic SS



      • Cellular clusters


      • Hyperchromatic, overlapping short ovoid nuclei


      • Inconspicuous nucleoli


      • Scanty cytoplasm


      • Mast cells, calcifications

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Synovial Sarcoma
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