Synovial sarcoma

Case contributed by Dr Mostafa El-Feky


Soft tissue swelling above the left knee.

Patient Data

Age: 30
Gender: Female

Left thigh

Soft tissue swelling and increased density over the lower medial aspect of the left femur with related supracondylar/medial lower distal femur shaft heterogenous bony density and intra-medullary irregular sclerotic line with rarefaction of the intervening bone cortex.


MRI of both thighs

An irregular infiltrative inter-muscular soft tissue mass is noted at the anteromedial aspect of the lower left thigh. It measures about 8.5x7x12.5 cm in maximum dimensions. The lesion is insinuated between and infiltrating the lower parts of the vastus medialis and intermedius muscles. The superficial femoral vessels are running along the posterior aspect of the lesion with relative intact fat planes.

It expresses heterogenous slightly hyperintense signals at T1, mixed intermediate and hyperintense signals at T2 and T2 fat sat with extensive intra and peri-lesional signal void vascular channels reflecting hypervascularity. Moderate heterogenous post-contrast enhancement.

The lesion invades the anteromedial aspect of the distal femoral shaft with frank cortical invasion and intra-medullary extension. Modest intra-articular extension to the superomedial aspect of the left knee joint cavity.

The right thigh and knee are essentially unremarkable.

Case Discussion

Such features are reflecting aggressive neoplastic inter-muscular lesion of the lower left thigh, pathologically proved synovial sarcoma (pathology report not available). Synovial sarcomas are intermediate to high grade malignant soft tissue tumors, most commonly located within the soft tissue surrounding the knee joint (70%). Direct bony invasion is seen in ~30% of cases. Metastasis is frequent to lungs (80%), bone (15 %) and lymph nodes. MRI is the modality of choice to stage the tumor locally, although imaging findings are not pathognomonic.

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Case information

rID: 57692
Published: 19th Jan 2018
Last edited: 20th Jan 2018
Inclusion in quiz mode: Included
Institution: Dar El Ashaa Center

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