Which MRI findings are characteristic of synovial sarcoma?

Updated: Mar 02, 2019
  • Author: Michael J Duh, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Synovial sarcoma tumors tend to be large, averaging approximately 8 cm in their largest dimension, which is usually parallel to the long axis of the body. Approximately 91% of patients have a well-defined, ovoid lesion with rounded or gently lobulated margins (see the image below). [24] The effect on adjacent structures is usually displacement, rather than invasion or destruction. [9]  

Axial T1-weighted magnetic resonance image of the Axial T1-weighted magnetic resonance image of the thigh in a 45-year-old man who presented with a large, right midthigh mass. The anterior mass is well circumscribed, with mostly homogeneous isointensity relative to the muscle. Scattered, small, hyperintense foci probably represent hemorrhage. The fat plane between the mass and the femur is preserved.

Most tumors display a heterogeneous intermediate signal intensity on T1-weighted MRIs. Lesions smaller than 5 cm are more likely to have a predominantly homogeneous signal intensity that is similar to that of the adjacent muscle (as in the above image). Larger lesions are most often heterogeneous secondary to extensive areas of hemorrhage and necrosis, a characteristic seen in the image below.

Sagittal T1-weighted magnetic resonance image of t Sagittal T1-weighted magnetic resonance image of the thigh in a patient with a mass in the anterior left upper thigh and/or inguinal region. The image shows large areas of hemorrhage and necrosis, with intermediate signal intensity on a background of a muscle-intensity mass.

On T2-weighted images, lesions are usually hyperintense, with a signal intensity similar to or higher than that of fatty tissue (as in the first image below). Considerable inhomogeneity is demonstrated in 82% of lesions, with cystic components seen in 77% (as demonstrated in the second and third images below). Cystic components with striking fluid-fluid levels are demonstrated in 18% of tumors. [24]

Sagittal T2-weighted magnetic resonance image of t Sagittal T2-weighted magnetic resonance image of the foot in a 60-year-old man who presented with a mass on the dorsum of his left foot. The mass shows predominantly high signal intensity that is hyperintense relative to fat. Scattered areas of hypointensity probably represent calcifications.
Coronal T2-weighted magnetic resonance image of th Coronal T2-weighted magnetic resonance image of the thigh in a 45-year-old man who presented with a large midthigh mass on the right. On this T2-weighted image, the mass has become markedly heterogeneous, with high signal intensity depicting cystic regions of hemorrhage and necrosis. Note that portions of the mass are hyperintense relative to the subcutaneous fat. The location of the mass is somewhat atypical because it is centered at the level of the midshaft rather than near a joint.
Axial T2-weighted magnetic resonance image of the Axial T2-weighted magnetic resonance image of the hip in a patient with a mass in the anterior left upper thigh and/or inguinal region. The mass is inseparable from the underlying femoral cortex and contains strikingly hyperintense cystic areas with irregular septa of intermediate signal intensity.

Approximately one third of lesions demonstrate the "triple signal pattern" on T2-weighted images; this pattern consists of a combination of (1) hyperintense fluid within cystic components, with or without fluid levels, (2) intermediate signal tissue similar in intensity to that of muscle, and (3) slightly hypointense tissue similar in intensity to that of fibrous tissue.

Apposition to bone surfaces without a clear plane of separation is seen in 50-59% of cases, with clear bone erosion (as seen in the superior talus in the image below) or destruction in 22%. Calcifications are not easily seen on MRIs and, when visible, are usually hypointense on all sequences.

Coronal T1-weighted magnetic resonance image of th Coronal T1-weighted magnetic resonance image of the foot in a 60-year-old man who presented with a mass on the dorsum of his left foot. A rounded, soft-tissue mass is seen eroding the cortex of the superior talus. The mass is predominantly isointense relative to the muscle, with scattered areas of hyperintensity that are consistent with hemorrhage.

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