Synovial sarcoma
Updates to Article Attributes
Synovial sarcomas are relatively common intermediate to high grade malignant soft tissue tumour often with an initial indolent course.
Epidemiology
Synovial sarcomas typically present in adolescents and young adults (15-40 years of age). There may be a mild (M:F 1.2:1) male predilection.
Clinical presentation
Presentation is most often with a slowly enlarging soft tissue mass which may have been noted for a number of years and gives a false impression of a benign process4.
The most common location for these tumours is within the soft tissues adjacent to large joints, e.g the knee and popliteal fossa. While these tumour arise near joints, it is rare form them to arise from the joint itself and despite their name, they do not arise from synovial structures, e.g. joints, tendon sheaths and bursae.
Pathology
Synovial sarcomas account for 2.5-10% of all soft tissue sarcoma 2-4. Its name is derived from the fact that microscopically it resembles normal synovium, however it stains for epithelial markers (e.g. epithelial membrane antigen and cytokeratin) which synovium does not. Additionally it has been found in many locations that does not have normal synovium.
Macroscopically they have non-specific appearances. They are well or poorly defined heterogeneous masses with frequent areas of haemorrhage and necrosis.
They are divided histologically into 4 sub types:
- biphasic: 20-30%
- monophasic fibrous: 50-60%
- monophasic epithelial: very rare
- poorly differentiated: 15-25%
Cytogenetic aberration of the t(X;18) translocation is highly specific, seen in over 90% of cases1-4.
Location
- extremities: 80-95% 1
- lower limb: 60-70%
- upper limb: 15-25%
- from soft tissues: 90-95%
- from joint: 5-10%
- head and neck: 5%
- hypopharynx or parapharyngeal space
- conjunctiva 3
- CNS
- chest wall: rare 6
- viscera: rare
- lung 2, kidney, prostate, oesophagus, heart, pericardium, pleura
Radiographic features
A soft tissue mass near but not in a joint in a young patient (15-40 years old), particularly if calcification is present , are very suggestive.
Plain film
X-rays may be normal, unless the mass is large or contains dystrophic calcification, which are found in up to 30% of cases 1. These calcifications are non-specific within the periphery of the lesion and not usually osteoid or chondroid in appearance.
Occasionally smooth pressure erosions may be visible on the underlying bone, which should not be mistaken for a sign of a benign process.
Alternatively frank bony invasion is seen in 11-50% of cases, with aggressive bony features (permeative, geographic, or moth-eaten appearances) 4.
Ultrasound
Non-specific findings, with a heterogeneous predominantly hypoechoic mass.
CT
Similarly CT is non-specific demonstrating a soft tissue mass of heterogenousheterogeneous density and enhancement. CT is of course more sensitive to calcifications that either x-rays or MRI.
MRI
MRI is the modality of choice to locally stage the tumour, although again imaging findings are not pathognomonic. The mass is usually large and variably well-defined (smaller lesions tend to be better circumscribed).
-
T1
- iso- (slightly hyper-) intense to muscle
- heterogeneous
-
T2
- mostly hyperintense
- markedly heterogeneous appearance of synovial cell sarcomas on fluid sensitive sequences result in so called " triple sign" which is due to areas of necrosis and cystic degeneration with very high signal, relatively high signal soft tissue components, and areas of low signal intensity due to dystrophic calcifications and fibrotic bands
. - due to high tendency of lesions to bleed, there might be areas of fluid-fluid levels known as "bowel of grapes" are seen in up to 10-25% of cases
-
T1 C +
- enhancement is usually prominent and can be diffuse (40%) heterogeneous (40%) or peripheral (20%) 1
Bone scan
Typically synovial sarcomas have heterogeneously increased dynamic and blood pool uptake, with some increase in delayed images, but usually less intense.
Angiography / DSA/DSA
Is not usually performed. These tumours are usually hypovascular 1.
Treatment and prognosis
Treatment involves a combination of surgery and usually adjuvant radiotherapy +/- chemotherapy. Radiotherapy is particularly useful in treating tumours where an adequate clear margin cannot be achieved, and ideally radiotherapy is administered pre-operatively.
Good prognostic variables include:
- small size
- located in extremity
- younger age <
; 20;20 years of age - solid homogenous mass
- presence of calcification
- biphasic histology (controversial)
Poor prognostic variables include:
- large size (>5 cm): most important factor
- located in the trunk or head and neck
- older patients
- cystic/haemorrhagic components
- marked heterogeneity
- histology
- poorly differentiated histology
- rhabdoid cells
- extensive tumor necrosis
- high nuclear grade
- p53 mutations
- high mitotic rate (>10 mitoses per 10 high-power field)
Overall 5 year survival is between 36-76% with both local recurrence (30-50%) and distant metastases (40%) being common.
Differential diagnosis
General imaging differential considerations include:
-</ul><h4>Radiographic features</h4><p>A soft tissue mass near but not in a joint in a young patient (15-40 years old), particularly if calcification is present , are very suggestive.</p><h5>Plain film</h5><p>X-rays may be normal, unless the mass is large or contains dystrophic calcification, which are found in up to 30% of cases <sup>1</sup>. These calcifications are non-specific within the periphery of the lesion and not usually osteoid or chondroid in appearance. </p><p>Occasionally smooth pressure erosions may be visible on the underlying bone, which should not be mistaken for a sign of a benign process. </p><p>Alternatively frank bony invasion is seen in 11-50% of cases, with aggressive bony features (permeative, geographic, or moth-eaten appearances) <sup>4</sup>. </p><h5>Ultrasound</h5><p>Non-specific findings, with a heterogeneous predominantly hypoechoic mass. </p><h5>CT</h5><p>Similarly CT is non-specific demonstrating a soft tissue mass of heterogenous density and enhancement. CT is of course more sensitive to calcifications that either x-rays or MRI. </p><h5>MRI</h5><p>MRI is the modality of choice to locally stage the tumour, although again imaging findings are not pathognomonic. The mass is usually large and variably well-defined (smaller lesions tend to be better circumscribed). </p><ul>- +</ul><h4>Radiographic features</h4><p>A soft tissue mass near but not in a joint in a young patient (15-40 years old), particularly if calcification is present , are very suggestive.</p><h5>Plain film</h5><p>X-rays may be normal, unless the mass is large or contains dystrophic calcification, which are found in up to 30% of cases <sup>1</sup>. These calcifications are non-specific within the periphery of the lesion and not usually osteoid or chondroid in appearance. </p><p>Occasionally smooth pressure erosions may be visible on the underlying bone, which should not be mistaken for a sign of a benign process. </p><p>Alternatively frank bony invasion is seen in 11-50% of cases, with aggressive bony features (permeative, geographic, or moth-eaten appearances) <sup>4</sup>. </p><h5>Ultrasound</h5><p>Non-specific findings, with a heterogeneous predominantly hypoechoic mass. </p><h5>CT</h5><p>Similarly CT is non-specific demonstrating a soft tissue mass of heterogeneous density and enhancement. CT is of course more sensitive to calcifications that either x-rays or MRI. </p><h5>MRI</h5><p>MRI is the modality of choice to locally stage the tumour, although again imaging findings are not pathognomonic. The mass is usually large and variably well-defined (smaller lesions tend to be better circumscribed). </p><ul>
-<li>markedly heterogeneous appearance of synovial cell sarcomas on fluid sensitive sequences result in so called " <a href="/articles/triple-sign">triple sign</a>" which is due to areas of necrosis and cystic degeneration with very high signal, relatively high signal soft tissue components, and areas of low signal intensity due to dystrophic calcifications and fibrotic bands.</li>- +<li>markedly heterogeneous appearance of synovial cell sarcomas on fluid sensitive sequences result in so called " <a href="/articles/triple-sign">triple sign</a>" which is due to areas of necrosis and cystic degeneration with very high signal, relatively high signal soft tissue components, and areas of low signal intensity due to dystrophic calcifications and fibrotic bands</li>
-</ul><h5>Bone scan</h5><p>Typically synovial sarcomas have heterogeneously increased dynamic and blood pool uptake, with some increase in delayed images, but usually less intense. </p><h5>Angiography / DSA</h5><p>Is not usually performed. These tumours are usually hypovascular <sup>1</sup>. </p><h4>Treatment and prognosis</h4><p>Treatment involves a combination of surgery and usually adjuvant radiotherapy +/- chemotherapy. Radiotherapy is particularly useful in treating tumours where an adequate clear margin cannot be achieved, and ideally radiotherapy is administered pre-operatively. </p><p>Good prognostic variables include:</p><ul>- +</ul><h5>Bone scan</h5><p>Typically synovial sarcomas have heterogeneously increased dynamic and blood pool uptake, with some increase in delayed images, but usually less intense. </p><h5>Angiography/DSA</h5><p>Is not usually performed. These tumours are usually hypovascular <sup>1</sup>. </p><h4>Treatment and prognosis</h4><p>Treatment involves a combination of surgery and usually adjuvant radiotherapy +/- chemotherapy. Radiotherapy is particularly useful in treating tumours where an adequate clear margin cannot be achieved, and ideally radiotherapy is administered pre-operatively. </p><p>Good prognostic variables include:</p><ul>
-<li>younger age < 20 years of age</li>- +<li>younger age <20 years of age</li>
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