Synovial sarcoma accounts for 5-10% of all soft tissue sarcomas. It is more common in young and middle-aged people aged 15 to 40 years, and is more common in men than women. At present, it is believed that synovial sarcoma is not a malignant tumor occurring in synovial tissue. Currently, WHO classification of soft tissue sarcoma classifies it as a malignant tissue tumor of uncertain type, and some scholars suggest renaming it as carcinosarcoma or soft tissue spindle cell carcinoma.
1.Clinical manifestations.
Synovial sarcoma is usually found in the extremities, mostly manifested as deep palpable masses with occasional pain or tenderness. Trauma may induce the tumor.
2.Imaging manifestations.
Most of the masses are accompanied by calcification, and small dotted calcification can be seen on X-ray. In some patients, MRI examination can show a mixture of hemorrhage, necrosis and tumor, which is called “pebble sign” or “triphasic sign”, which is helpful for diagnosis.
3.Pathology.
There are four types of synovial sarcoma: biphasic, monophasic fibrous, monophasic epithelial, and hypofractionated.
Immunohistochemistry of the tumor shows positive expression of multiple epithelial and mesenchymal tissue markers, and the diagnosis of specific subtypes relies on microscopic presentation and immunohistochemistry. 1/3 of patients have SYT-SSX2 fusion gene, and 2/3 of patients have detectable SYT-SSX1 fusion gene.
Most of the tumors carrying SYT-SSX2 are monophasic fibrous type, while SYT-SSX1 is mostly seen in biphasic synovial sarcoma.
4. Differential diagnosis.
The differential diagnosis of biphasic synovial sarcoma includes: malignant peripheral nerve sheath tumor, malignant salamander tumor, malignant mesothelioma, etc.
The differential diagnosis of monophasic fibrous synovial sarcoma includes: fibrous sarcoma, smooth muscle sarcoma, etc.
Monophasic epithelial type synovial sarcoma: adjuvant carcinoma or metastatic carcinoma, etc.
Differential diagnosis of hypodifferentiated synovial sarcoma: rhabdomyosarcoma, neuroblastoma, malignant hemangioepithelioma, mesenchymal soft tissue sarcoma, lymphangioleiomyosarcoma.
5. Recurrence and metastasis.
Although synovial sarcoma is malignant, its recurrence and metastasis rates are decreasing with the improvement of treatment. Surgical resection is the treatment of choice, and sufficiently extensive expansion of resection or adjuvant radiotherapy can significantly reduce the recurrence rate. The most common site of metastasis is the lung, followed by lymph nodes and bone. The rate of metastasis has been reported to be 94% in the lungs and 10% in the lymph nodes. Although advanced metastasis occurs, most of them can survive with tumor for a long time.
6. Prognosis.
The 5-year survival rate of synovial sarcoma is 36-76%, but the 5-year survival rate of extensively calcified tumor is as high as 82%. 10-year survival rate is 20-63%. The prognosis of SYT-SSX2 type tumor is twice as long as that of SYT-SSX1 type.
7.Treatment.
1. Whether the initial resection range is sufficient is crucial. Some scholars have pointed out that local excision of tumor and supplemented with radiotherapy is better than amputation surgery.
2.Synovial sarcoma is a chemotherapy sensitive tumor, commonly used drugs include: isocyclophosphamide, adriamycin or epirubicin, 50% of tumors are partially or fully effective for drugs.
3, Immunohistochemistry EGFR(+) can be used gefitinib, Her2(+) may be sensitive to Herceptin treatment.