A synovial sarcoma (also known as malignant synovioma[1]) is a rare form of cancer which occurs primarily in the extremities of the arms or legs, often in proximity to joint capsules and tendon sheaths.

[4][2] Synovial sarcoma usually presents with an otherwise asymptomatic swelling or mass, although general symptoms related to malignancies can be reported such as fatigue.

[5] The diagnosis of synovial sarcoma is typically made based on histology and is confirmed by the presence of t(X;18) chromosomal translocation.

Synovial sarcoma can also appear to be poorly differentiated or to be monophasic fibrous, consisting only of sheets of spindle cells.

Some authorities[3] state that, extremely rarely, there can be a monophasic epithelial form which causes difficulty in differential diagnosis.

[15] Treatment is usually multimodal, involving surgery, chemotherapy and radiotherapy:[16] Afamitresgene autoleucel (Tecelra) was approved for medical use in the United States in August 2024.