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Introduction Synovial Sarcoma (SS) is a mesenchymal malignant tumor It represent 5 to 10% of soft tissues tumors Two features associated with synovial sarcoma that may lead to
an initial mistaken diagnosis of a benign indolent process are slow growth (average time to diagnosis, 2–4 years) and small size
Imaging has an important role in the assessment of this tumor
although appearance is not specific We present 11 observations of soft tissue Synovial Sarcoma of
limbs, emphasising their imaging characteristics with review of the literature
Patients and Methods
Since 1995, 11 observations of soft tissue Synovial Sarcoma of limbs have been detected.
All patients had radiographs, 2 were examined by high resolution ultrasound, 4 by CT and 9 by MRI.
6 women and 5 men were included in the study
The were aged between 13 to 64 years with a mean of 36 years
The lower limbs were involved in 9 cases: knee (n=5) , 1 in thigh (n= 1) leg (n= 1), ankle (n= 1) and foot (n= 1)
2 tumors were located in the upper limb: forearm (n= 1), shoulder (n= 1).
9 Synovial Sarcoma had a juxta-articular location.
2 were located in soft tissues of leg and in that of thigh, away from the joint.
The size of the tumors ranged from 4 to 14 cm with an average
of 7.8 cm.
Results : Radiographs Radiographs showed a soft tissue mass, associated with calcifications in 3 cases, osteolysis in 2 cases, unilamellar periosteal reaction in one case, and bone condensation facing the mass in one case
Radiographs Fig.1 and 2: Juxta-articular calcified soft tissue mass. Fig. 3
Fig. 3: Juxta-articular soft tissue mass with osteolysis and periosteal new bone formation of radius.
Results : Ultrasound Ultrasound showed echoic and heterogenous appearance, sometimes with calcifications with increased Doppler Fig. 5 signal.
Fig. 4 and Fig. 5: Ultrasound of the knee heterogenous solid mass of the infrapatellar knee region with increased Doppler Signal.
Results : CT Scan CT confirmed showed a solid soft tissue mass in three cases and a multiloculated cystic mass in one case. Calcifications within lesions were observed in two patients and a bone lesion in 3 patients. Fig. 6
Fig. 6 (Same case as Fig and 5) transversal CT view of the knee in soft tissue algorithm:
solid infrapatellar soft tissue mass containing coarse calcifications, and infiltrating the subcutaneous tissue.
Results : MRI
On MRI, the tumor had well defined margins in all cases
In 8 patients, MRI signal intensity was intermediate to low compared to muscle on T1, high on T2, with heterogenous enhancement after IV Gadolinium injection
In 4 patients, the signal was high and heterogenous on T2 with a "triple signal" appearance
In one case, there was a multiloculated cystic appearance: Low intensity signal on T1, high intensity signal on T2 with internal septa enhancement after injection
In 4 patients an associated bone lesion was revealed by MRI
Axial T1-weighted image
Sagittal T2-weighted image
Fig. 7 and Fig. 8: Well defined mass with a low signal on T1 weighted images and a heterogenous high signal on T2 weighted images.
Fig. 11: Axial T2-weighted image Fig. 9 and Fig. 10: Sagittal T1-weighted image before and after IV Gadolinium injection Soft tissue mass having an intermediate signal (similar to muscle) on T1 (Fig. 9), heterogenous high signal on T2 (Fig. 11) and a heterogenous enhancement after IV Gadolinium injection (Fig. 10)
Fig. 12: Sagittal T2-weighted image, "Triple signal" appearance
Fig. 13: Sagittal T1-weighted image
Fig. 14: Sagittal T2-weighted image
Synovial Sarcoma of the knee with Cystic appearance on MRI : low T1 (Fig. 13) and high T2 signal (Fig. 14)
Discussion : Epidemiology 4th most frequent soft tissue neoplasms representing 2.5 to
10% [1,2] Occurs mainly in young adults : 15 – 40 years old 80%–95% of synovial sarcomas occur in the limbs. 60%–71% lower limb 16%–25% upper limb [1,4,5,6,7] Despite its name, less than 10% of SS arise within a joint Mostly adjacent (40%–50% ) or nearby (60%–75%)a joint
space, with a mean diatance of 5 cm. Intra-articular involvement is more commonly due to the extension of a juxta-articular neoplasm [1-2-3].
Discussion : Pathology Synovial sarcoma is an intermediate to high grade tumor. There are three main histologic subtypes of synovial sarcoma:
biphasic (20%-30%), monophasic(50-60%), and poorly differentiated (15-25%) [1,8]. Grading of synovial sarcoma is achieved by applying the grading
scheme for all sarcomas by the FNCLCC (French Federation Nationale des Centres de Lutte Contre le Cancer) : degree of differentiation, mitotic activity, and necrosis. The cytogenetic aberration of the t(X;18) translocation is highly
specific for synovial sarcoma [1,23]. : Observed in 90% of synovial sarcoma Not found in other tumors
Discussion : Radiographs Radiographs are normal in 50% of cases Otherwise they typically show nonspecific, round to oval
juxta-articular soft-tissue masses Calcifications are identified in up to 30% of synovial
sarcomas. These are often eccentric or peripheral within and nonspecific in appearance [1,9] Extrinsic bone erosions or periosteal new bone formation
have been reported in 11%–20% of cases Aggressive bone invasion is far less common (5% of cases)
Discussion : Ultrasound The US appearance of synovial sarcoma: In 66% of cases: focal, nodular, round or lobulated, solid
hypoechoic soft-tissue mass
In 14%: prominent heterogeneity with irregular margins 20% of cases: complex sonographic appearance Doppler US demonstrates vascularity in the areas of viable
Discussion : CT Is not a good imaging modality for the assessment of soft tissue
tumors. Non specific appearance : heterogenous multinodular soft-tissue mass Areas of lower attenuation representing necrosis or hemorrhage are
also common (1,9,11) Interesting to show calcifications
( 27%–41%) and adjacent bone
abnormalities ( nearly 25% of lesions) A cystic form had been described in a minority of cases (12,24)
Discussion : MRI Is the method of choice in the assessment of soft tissue tumors On T1-weighted MR images: heterogeneous multilobulated soft tissue
mass with intermediate to low signal
On T2-weighted MR images:
heterogeneity with predominant high
signal intensity (1,22), sometimes a multilobulated mass with intervening septa. The enhancement is more commonly heterogeneous (83%–100%) than
homogeneous (0%– 17%). It may be diffuse, Peripheral, nodular , with or without thick septa in
largely necrotic lesions
Discussion : MRI Areas of haemorrhage, are seen as fluid levels or foci of high signal
intensity on T1- and T2-weighted MR images (47%) The triple sign: Described by Jones et al (see Fig 12)
- Is the result of intermixed areas of low (calcified or fibrotic collagenized regions), intermediate (solid cellular elements), and high signal intensity on T2 (hemorrhage or necrosis) - It has been described as occurring in 35%–57% of cases but also seen in other soft-tissue neoplasms (1,21,22) Bone involvement, manifested either by cortical erosion or invasion of
the marrow space (21% )
Frequently invade adjacent muscle
Discussion : MRI Diffusion shows an increased signal in benign soft tissue masses
compared to their malignant counterparts, whereas the ADC
values between these groups are not significantly different. This difference can be explained by the contribution of perfusion to the ADC values .
The dynamic contrast-enhanced MR imaging appearance of
synovial sarcoma may be a rapid progressive linear increase in signal intensity followed by washout or plateau (60%), or a late
sustained increase in enhancement after the initial rapid enhancement (40%) 
Discussion : PET and SCINTIGRAPHY Scintigraphic evaluation reveal prominent increased
uptake. It has an important role in the detection of possible metastatic disease and in monitoring response to therapy [1,25] Positron emission tomography demonstrates marked
increased tracer accumulation [1,10]
Discussion : Criteria for imaging grading Statistically significant imaging features that favored a high Grade synovial sarcoma Absence of calcification Presence of cystic components Presence of hemorrhage Presence of the triple sign
Imaging findings that were seen only with high-grade lesions : Cystic components Hemorrhage Fluid levels The triple sign 
Discussion : Treatment The current treatment of choice is wide local excision : The surgical margins should be closely evaluated to
determine the need for adjuvant therapy Amputation should be reserved for those cases in which gross resection of the tumour and preservation of a functional limb is not possible 
Radiation therapy plays an important role in the treatment of
marginally resected tumours Initiated preoperatively if the surgeon believes that the surgical margins will be positive or close If the margins are microscopically positive, radiation should be given postoperatively [1,14,15]
Discussion : Post treatment Imaging Increasing signal intensity on T2-weighted MR images may
be seen within the synovial sarcoma after chemotherapy or radiation therapy but does not mean recurrence Tumor size may also show a reduction in response to this
therapy Oedema surrounding the tumour, typically not a
significant feature before therapy, may also develop subsequent to adjuvant treatment
Discussion : Local recurrence and Metastasis The clinical course of synovial sarcoma is characterized by a high rate of
local recurrence and metastatic disease. Local recurrence following resection occurs in 30%– 50% of patients, and
distant metastasis in 41%  The most frequent metastatic site is the lung (94%), followed by lymph
nodes (4%–18%) and bone (8%–11%) Metastases are present in 16%–25% of patients at their initial presentation
 The majority of metastases occur within the first 2–5 years after treatment
Late metastases may occur up to 26 years after the initial diagnosis, which
reduces the 10-year versus 5-year survival rates
Discussion : Prognosis factors Clinical and pathologic factors having prognostic significance : Age: < 15–20 years is also associated with a better long-term prognosis Location in the extremities: more favourable prognosis Tumour size: greater than 5 cm at presentation has the greatest impact
(64% vs 26% 5 years survival rates) The presence of extensive calcifications: suggests improved long-term survival, with 5-year survival rates of 82% and decreased rates of local recurrence (32%) and metastatic disease (29%) (1,16,18,19) Other factors: Degree of differenciation
high nuclear grade More recently, the gene fusion type SYT-SSX2 (more common in
monophasic lesions) has been associated with an improved prognosis (compared with that for SYT-SSX1, and an 89% metastasis-free survival).
CONCLUSION Synovial sarcoma is the fourth most common malignant primary
Although the radiographic and ultrasonographic signs of
synovial sarcoma are not specific, the presence of a soft-tissue mass, nearby a joint in a young patient is very suggestive of this diagnosis
MRI is the method of choice for staging extent and surgical
Local recurrence and metastatic disease are common and
prognosis is guarded
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