Synovial Sarcoma Workup

Updated: Sep 24, 2018
  • Author: Bernardo Vargas, MD; Chief Editor: Omohodion (Odion) Binitie, MD  more...
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Workup

Laboratory Studies

Cytogenetic analysis aids the physician in detecting the specific chromosomal translocation between chromosome 18 and chromosome X—namely, t(X;18)(p11;q11). [22, 23, 24] This translocation produces the SYT-SSX1, SYT-SSX2, or SYT-SSX4 fusion gene. Identification of this anomaly is obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) in tumor tissue (and possibly in blood), [7, 8, 25] with a sensitivity of 96% and specificity of 100%. Fusion transcripts can be detected with molecular diagnostic techniques in biopsy samples.

Fluorescence in-situ hybridization (FISH) is less expensive than RT-PCR. It has been suggested as a good method of first choice for synovial sarcoma (also referred to as synovial cell sarcoma). [25] This method has a lower sensitivity than RT-PCR does, but the results of the two methods are concordant in 76% of cases.

Aside from molecular diagnostic tests, no laboratory studies are specific for this diagnosis.

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Imaging Studies

Plain radiography

Plain radiographs may aid in the diagnosis. Synovial sarcoma typically produces a spotty calcification (snowstorm) within the matrix of the soft-tissue tumor that may be visualized on plain radiographs (see the image below).

Lateral radiograph depicts a synovial sarcoma of t Lateral radiograph depicts a synovial sarcoma of the dorsum of the hand. A small nodule, present for 5 years, rapidly enlarged to the present size over 2 months.

Computed tomography

Computed tomography (CT) is used to confirm the presence of a mass, its size, and its location, but it is nondiagnostic. It also may detect secondary bony involvement, which is not uncommon with larger synovial sarcomas. Synovial sarcoma is a malignant disease; therefore, CT of the chest is mandatory to exclude metastatic disease.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is the investigation of choice for soft-tissue sarcomas. Low signal intensity is observed on T1-weighted MRI (see the first image below), and high signal intensity is observed on T2-weighted MRI (see the second image below). The signal from the matrix is fairly homogeneous unless calcification is present.

T1-weighted MRI depicts a synovial sarcoma of the T1-weighted MRI depicts a synovial sarcoma of the dorsum of the hand. The tumor has low signal on T1 weighting.
T2-weighted MRI depicts a synovial sarcoma of the T2-weighted MRI depicts a synovial sarcoma of the dorsum of the hand. The tumor has a heterogeneous signal on T2 weighting, indicative of a variable growth pattern.
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Histologic Findings

The histologic picture of synovial sarcoma can be confused with those of many other round blue cell tumors. Macroscopically, the tumor is a grayish-white and often has a greasy feel. Histologic features of synovial sarcoma are identical in children and adults.

Three types of synovial sarcoma have been described, as follows:

  • In the monophasic type, there is a predominance of spindle cells, mixed with round cells (see the image below); cells are arranged in fascicles with a poorly defined cytoplasm; no glandular areas are present
  • The biphasic type has a layer of columnar epithelium in addition to spindle cells; it consists of plump, round cells and spindle-shaped fibroblasts alternating with glandular-like areas that are lined by synovial-like cells and contain mucin
  • A third type, called poorly differentiated, has numerous mitosis, high cellularity, and tumor necrosis
Although synovial sarcoma typically has a biphasic Although synovial sarcoma typically has a biphasic histology, this disease is often monophasic (lacking glandular differentiation), which produces the picture of a small, round blue cell tumor.

The histologic grade is determined by a score of the mitotic activity and tumor necrosis, ranging from grade 1 (differentiated) to grade 3 (poorly differentiated). Synovial sarcoma is very often associated with a grade 2 or grade 3. [12, 6, 7, 26] Punctuate areas of calcification may be observed.

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Staging

Staging requires local imaging with MRI. The most likely site of distant spread, the lungs, can be observed by means of CT. Synovial sarcoma is a high-grade lesion.

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