Updated: 6/22/2021

Synovial Sarcoma

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https://upload.orthobullets.com/topic/8052/images/Case B - axilla - xray - parsons_moved.jpg
https://upload.orthobullets.com/topic/8052/images/Case B - axilla - MRI - parsons_moved.jpg
https://upload.orthobullets.com/topic/8052/images/Case A - pelvis - xray - parsons_moved.jpg
https://upload.orthobullets.com/topic/8052/images/Case A - pelvis - CT - parsons_moved.png
https://upload.orthobullets.com/topic/8052/images/Histology B - Parsons_moved.png
https://upload.orthobullets.com/topic/8052/images/synovial-sarcoma-25-sarcoma-images_moved.jpg
  • summary
    • Synovial Sarcoma is a malignant, soft tissue sarcoma caused by a t(X;18) chromosomal translocation mutation most commonly found near joints, but rarely within the joint.
    • The condition usually presents in patients between 15 and 40 years old with a growing mass in proximity to a joint.
    • Diagnosis is made with a biopsy showing a classic biphasic appearance with atypical spindle cells and epithelial cells. Immunostaining is positive for epithelial membrane antigen and vimentin. 
    • Treatment is usually wide surgical excision with radiation. 
  • Epidemiology
    • Demographics
      • most common sarcoma found in young adults (15-40 years)
      • affects more males than females
    • Anatomic location
      • it is the most common malignant sarcoma of the foot
  • Etiology
    • Mechanism
      • cellular origin of synovial sarcoma is unknown, but it is not the synovial cell or any cell involved in the synovium
        • the name synovial sarcoma is a misnomer.
    • Pathophysiology
      • metastasis
        • synovial sarcoma typically shows high histologic grade
        • metastasis may develop in 30-60% of patients
          • like other sarcomas, the lung is most common site of metastasis
          • synovial sarcoma is one of the rare soft tissue sarcomas which can metastasize to lymph nodes
            • the other sarcomas which can metastasize to lymph nodes include
              • angiosarcoma
              • clear cell sarcoma
              • rhabdomyosarcoma
              • epithelioid sarcoma
            • can stage with lymph node biopsy
              • while lymph node metastasis is a poor prognostic sign, it is not as bad as lung metastasis
        • metastasis is more common with large, deep, and high grade sarcomas
    • Genetics
      • chromosomal translocation t(X;18) is observed in more than 90% of cases
      • translocation forms the SYT-SSX1, 2, or 4 fusion protein
        • SYT-SSX4 is rare
    • SYT-SSX1 vs. SYT-SSX2
      SYT-SSX1
      SYT-SSX2
      Frequency
      More common (60% of tumors)
      Less common (40% of tumors)
      Histology type
      Biphasic
      Monophasic
      Gender
      M:F = 1:1
      M:F = 1:2
      Presentation
      Larger, with metastases
      Smaller, without metastases
      Survival
      Worse
      Better
  • Presentation
    • Symptoms
      • typically present as a growing mass in proximity to a joint
      • may be painless or painful
      • most commonly occur in periarticular locations
        • knee, shoulder, elbow, foot
        • 60% are found in the lower extremity
    • Physical exam
      • check for regional lymphadenopathy
  • Imaging
    • Radiographs
      • can show soft tissue mineralization (calcification) in these tumors
      • may resemble heterotopic ossification
    • CT
      • can show calcification in the soft tissue mass
    • MRI
      • MRI reveals a heterogenous mass that is typically dark on T1 weighted images and bright on T2 weighted images
  • Histology
    • Characteristic findings
      • classical synovial sarcoma shows a biphasic appearance with two typical cell types
        • spindle cells (fibrous type of cells)
          • relatively small and uniform and found in sheets of malignant appearing cells with minimal cytoplasm and dark atypical nuclei
        • epithelial cells
          • gland, nest, or cyst-like cells
      • rarely, synovial sarcoma can also present with poorly differentiated or monophasic fibrous cell histology, consisting only of sheets of spindle cells
      • cellular origin of synovial sarcoma is unknown, but it is not the synovial cell or any cell involved in the synovium. The name SYNOVIAL sarcoma is a misnomer
    • Immunostaining for
      • synovial sarcoma stains positive for
        • vimentin
        • epithelial membrane antigen
        • sporadic S-100
        • epithelial cells stain positive for keratin
  • Treatment
    • Operative
      • wide surgical resection with adjuvant radiotherapy
        • indications
          • standard of care in most patients
        • technique
          • radiotherapy
            • may be delivered either pre-surgery or post-surgery
          • chemotherapy
            • data regarding chemotherapy in synovial sarcoma suggests that chemotherapy may improve both local control and overall survival
  • Prognosis
    • Overall prognosis is poor
      • 5 year survival is approximately 50%
      • 10 year survival is approximately 25%
    • SYT-SSX fusion type is most important prognostic factor 
      • SYT-SSX2 better survival

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(OBQ13.17) Which of the following tumors associated with the fusion protein SYT-SSX1 can metastasize via the lymph nodes?

QID: 4652
1

Alveolar rhabdomyosarcoma

3%

(128/4264)

2

Epitheliod sarcoma

4%

(171/4264)

3

Clear cell sarcoma

5%

(207/4264)

4

Angiosarcoma

2%

(104/4264)

5

Synovial sarcoma

85%

(3631/4264)

L 2 B

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(OBQ11.98) Which of the following fusion proteins is associated with synovial sarcoma?

QID: 3521
1

BCR-ABL

1%

(28/2448)

2

SYT-SSX

90%

(2212/2448)

3

EWS-FLI1

3%

(70/2448)

4

FUS-CHOP

2%

(49/2448)

5

COL1A1-PDGFB

3%

(74/2448)

L 1 C

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(OBQ08.236) All of the following statements regarding synovial sarcoma are correct EXCEPT?

QID: 622
1

Typically occur around the joints of the upper or lower limb

11%

(95/856)

2

Immunohistochemisty is positive for cytokeratin and epithelial membrane antigen

10%

(83/856)

3

Histology is named because the cell line of origin is the type II synovial cell

61%

(525/856)

4

May show biphasic or monophasic histology

7%

(61/856)

5

Classic age range is the younger adult < 40 years of age

10%

(83/856)

L 3 C

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(OBQ08.15) A 22-year-old female has a painful foot mass. Clinical photo, MRI, and histology slide are shown in Figures A through C. What is the most likely diagnosis?

QID: 401
FIGURES:
1

Osteosarcoma

1%

(24/2643)

2

Morton's neuroma

3%

(69/2643)

3

Synovial sarcoma

60%

(1591/2643)

4

Fibrous dysplasia

5%

(132/2643)

5

Desmoid tumor

31%

(817/2643)

L 3 C

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(OBQ05.72) Which of the following is the most common sarcoma found in the foot?

QID: 958
1

Epithelioid Sarcoma

12%

(363/3150)

2

Liposarcoma

2%

(69/3150)

3

Fibrosarcoma

8%

(244/3150)

4

Synovial sarcoma

77%

(2429/3150)

5

Adamantinoma

1%

(31/3150)

L 2 C

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(OBQ05.253) The chromosomal translocation t(X;18)is found in which of the following conditions?

QID: 1139
1

Myxoid liposarcoma

4%

(78/1875)

2

Synovial Sarcoma

83%

(1547/1875)

3

Osteosarcoma

3%

(50/1875)

4

Ewing's Sarcoma

7%

(122/1875)

5

Clear cell sarcoma

4%

(69/1875)

L 2 B

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(OBQ05.16) A 33-year-old male presents with a painful mass in his axilla. Radiographs, MRI, and histology are shown in Figures A-C. The tumor stains positive for vimentin and epithelial membrane antigen on immunohistochemistry. What is the most likely diagnosis?

QID: 53
FIGURES:
1

Synovial sarcoma

64%

(911/1414)

2

Liposarcoma

10%

(144/1414)

3

Malignant fibrous histiocytoma

22%

(314/1414)

4

Osteosarcoma

1%

(10/1414)

5

Chondrosarcoma

2%

(29/1414)

L 3 C

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(OBQ04.172) Which of the following histology images represents a synovial sarcoma?

QID: 1277
FIGURES:
1

Figure A

62%

(798/1289)

2

Figure B

2%

(30/1289)

3

Figure C

14%

(180/1289)

4

Figure D

9%

(113/1289)

5

Figure E

13%

(162/1289)

L 3 D

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