Synovial sarcoma is a rare and distinct type of cancer that affects the soft tissues of the body. While its name might suggest a connection to the synovial lining of joints, it originates from different cells and can appear in various locations. This form of cancer often presents unique challenges in diagnosis and treatment due to its subtle initial symptoms and specific genetic characteristics.
Defining Synovial Sarcoma
Synovial sarcoma is a rare soft tissue sarcoma, a type of cancer that develops in tissues supporting and connecting the body’s structures, such as fat, muscle, tendons, and nerves. Despite its name, this cancer does not originate from synovial cells, which line joints like the knee or elbow. Instead, it is believed to arise from primitive mesenchymal cells, which are a type of stem cell capable of developing into various connective tissues.
This cancer is considered uncommon, with approximately 1,000 cases reported annually in the United States. It typically affects adolescents and young adults, with the mean age of diagnosis around 30 years, and is slightly more common in males. A hallmark of synovial sarcoma is a specific genetic abnormality: a chromosomal translocation, most commonly t(X;18)(p11.2;q11.2). This translocation results in the fusion of the SYT gene (also known as SS18) on chromosome 18 with one of the SSX genes (SSX1, SSX2, or rarely SSX4) on the X chromosome, creating a fusion gene (SYT-SSX) that is crucial for the cancer’s development.
Recognizing Potential Indicators
Synovial sarcoma often presents with a noticeable lump or mass, which may or may not be painful. These tumors most frequently develop in the deep soft tissues near large joints, particularly in the lower extremities like the thigh or knee, but can also occur in the arms, feet, or even less common sites such as the head, neck, or abdomen. The lump might grow slowly and can go undetected for a significant period, sometimes a year or more, before symptoms become prominent.
As the tumor grows, it can cause other symptoms depending on its location. Swelling around the affected area is common. If the tumor presses on nerves, it might lead to pain, numbness, or weakness in the affected limb. When located near a joint, the tumor can restrict the range of motion or cause joint stiffness. These symptoms are not exclusive to synovial sarcoma, so medical evaluation is necessary for any persistent or concerning lumps.
Confirming a Diagnosis
The diagnostic process for synovial sarcoma begins with a thorough medical evaluation, including a physical examination and a review of the patient’s health history. Imaging techniques are then employed to visualize the tumor and assess its characteristics. Magnetic Resonance Imaging (MRI) is typically the preferred imaging tool, providing detailed images of the tumor’s size, exact location, and its relationship to surrounding tissues, muscles, and blood vessels. Computed Tomography (CT) scans may also be used to confirm the presence of a mass and for staging, especially to check for potential spread to the lungs, which is a common site for metastasis. Positron Emission Tomography (PET) scans can help determine if the cancer has spread to other parts of the body.
A definitive diagnosis of synovial sarcoma requires a biopsy, where a tissue sample from the tumor is removed for laboratory examination. This can be performed through a core needle biopsy or an incisional biopsy. Pathologists examine the tissue under a microscope, and specialized tests are crucial for confirmation. Immunohistochemistry, which uses antibodies to detect specific proteins, and molecular genetic testing are vital. The presence of the SYT-SSX fusion gene, resulting from the characteristic t(X;18) chromosomal translocation, is a highly specific marker used to confirm synovial sarcoma and distinguish it from other soft tissue tumors.
Pathways to Management
The management of synovial sarcoma typically involves a multidisciplinary approach, with a team of specialists collaborating to develop an individualized treatment plan. Surgery is often the primary treatment, aiming for complete removal of the tumor along with a margin of healthy tissue around it. Achieving clear margins is important to reduce the risk of local recurrence.
Radiation therapy is frequently used in conjunction with surgery. It can be administered before surgery to shrink the tumor, making it easier to remove, or after surgery to eliminate any remaining cancer cells and reduce the likelihood of the cancer returning in the same area. Chemotherapy may be considered, particularly for larger tumors, high-grade tumors, or if the cancer has spread to other parts of the body (metastatic disease), targeting cancer cells throughout the body. Recent advancements include targeted therapies and cellular therapies, such as afamitresgene autoleucel (Tecelra), which is an engineered T-cell therapy approved for advanced synovial sarcoma that targets specific markers like MAGE-A4 found in cancer cells. These newer treatments offer additional options, especially for cases that have not responded to conventional chemotherapy.