Synovial sarcoma is a rare type of soft tissue sarcoma. Commonly the tumor originates from the extremities, especially affecting the tissues around the knees. Synovial sarcoma is usually seen in teens, adolescents and young adults. Despite its name the tumor is not derived from the synovial, but it is called synovial due to the similarity of the tumor to the synovium. It is suggested that the tumor originates from the peripheral nerve sheath.
Synovial sarcomas comprise about 2,5-10% of all soft tissue sarcomas.
Males are more likely to develop this tumor (with a male to female ratio of 1,2:1).
About 80% of tumors arise in the limbs.
It is supposed that about 90% of cases are associated with a genetic mutation characterized by the switch between the X chromosome and chromosome 18 (t(X;18) translocation).The translocation event the SS18 gene on chromosome 18 and one of 3 SSX genes (SSX1, SSX2 and SSX4) on chromosome X results in the SS18-SSX fusion gene. This mutation is not inherited, but somatic.
There are several risk factors that increase the risk of developing synovial sarcoma such as:
Exposure to chemical carcinogens;
Neurofibromatosis type 1;
In the beginning the tumor may be asymptomatic. Slowly synovial sarcoma grows and becomes obvious. Later the symptoms of the tumor occur, they include:
Limited range of motion of the limb;
Numbness when the nerves are compressed;
When the tumor is located in the neck, it may cause difficulties swallowing;
The tumor tends to spread via lymphatic system and affect the lymph nodes;
Related: Kaposis sarcoma
Cytogenetic analysis is helpful to identify the genetic defects, which may contribute to the development of the tumor;
X-ray – sarcoma appears as a calcification in the tumor;
CT scan helps to verify the stage of the disease and detect the metastases;
Ultrasound examination to distinguish the tumor from bursitis, arthritis etc.;
MRI scan – “Triple Signal Intensity sign” is characteristic;
Bone scan to identify the neoplasm and metastases;
Biopsy to identify the type of the tumor, its grade and assess the malignancy. Histologically three types of synoviosarcoma are distinguished. The monophasic type is characterized by the presence of spindle cells with round cells, that are arranged in fascicles. The biphasic type is represented by an epithelium layer with spindle cells, which contain mucin. Poorly differentiated tumors have high cellularity, and tumor necrosis.
Surgery is the primary treatment. The whole tumor should be removed. In some cases, amputation is the only possible way to delete the sarcoma totally.
Radiation therapy (with a common dose of 40-60 Gy) is used to shrink the tumor before (neoadjuvant therapy) or after the surgery (adjuvant therapy) to target any remaining abnormal cells.
As radiotherapy, chemotherapy may be administered prior to surgery or after it.
Chemotherapy with administration of doxorubicin hydrochloride and ifosfamide is used to treat the metastatic disease.
Combinations of doxorubicin (75 mg/m2 by a continuous infusion over 3 days) and bolus ifosfamide (2.5 g/m2 daily for 4 days) are administered for the treatment of large tumors (bigger than 5 cm).
Granulocyte colony-stimulating factor (G-CSF) is used to stimulate the bone marrow.
The survival rate is 50-60% at 5 years after the diagnosis is made; 40-50% at 10 years.