Summary Synovial Sarcoma is a malignant, soft tissue sarcoma caused by a t(X;18) chromosomal translocation mutation most commonly found near joints, but rarely within the joint. The condition usually presents in patients between 15 and 40 years old with a growing mass in proximity to a joint. Diagnosis is made with a biopsy showing a classic mono/biphasic appearance with atypical spindle cells and epithelial cells. Immunostaining is positive for epithelial membrane antigen and vimentin. Treatment is usually wide surgical excision with radiation. Epidemiology Demographics 5-10% of all soft tissue sarcomas most common sarcoma found in young adults (15-40 years) affects males and females almost equally (1.2 to 1) More common in the lower limbs most commonly around the knee it is the most common malignant sarcoma of the foot Etiology Mechanism cellular origin of synovial sarcoma is unknown, but it is not the synovial cell or any cell involved in the synovium the name synovial sarcoma is a misnomer. Pathophysiology metastasis synovial sarcoma typically shows high histologic grade metastasis may develop in 30-60% of patients like other sarcomas, the lung is most common site of metastasis synovial sarcoma has been shown to have similar rates of lymph node metastasis compared to other soft tissue sarcomas i.e angiosarcoma, clear cell sarcoma, rhabdomyosarcoma, eithelioid sarcoma can stage with lymph node biopsy while lymph node metastasis is a poor prognostic sign, it is not as bad as lung metastasis metastasis is more common with large, deep, and high grade sarcomas Genetics chromosomal translocation t(X;18) is observed in more than 90% of cases translocation forms the SYT-SSX1, 2, or 4 fusion protein SYT-SSX4 is rare SYT-SSX1 vs. SYT-SSX2 SYT-SSX1 SYT-SSX2 Frequency More common (60% of tumors) Less common (40% of tumors) Histology type Biphasic Monophasic Gender M:F = 1:1 M:F = 1:2 Presentation Larger, with metastases Smaller, without metastases Survival Worse Better Presentation Symptoms typically present as a slow growing mass in proximity to a joint may be painless or painful most commonly occur in periarticular locations knee, shoulder, elbow, foot 60% are found in the lower extremity Physical exam check for regional lymphadenopathy Imaging Ultrasound nonspecific heterogenous hypoechoic mass Radiographs can show soft tissue mineralization (calcification) in these tumors may resemble heterotopic ossification CT Well circumscribed mass can show calcification in the soft tissue mass CT chest for staging MRI Gold standard for diagnostic imaging MRI reveals a heterogenous mass that is typically dark on T1 weighted images and bright on T2 weighted images T2 "triple sign" areas of high signaling form necrosis/cystic degeneration and low signaling from calcifications and fibrosis Staging Biopsy incisional (gold standard), Core needle of FNA CT Chest PET/CT Scan Histology Characteristic findings classical synovial sarcoma shows a mono/biphasic appearance with two typical cell types spindle cells (fibrous type of cells) relatively small and uniform and found in sheets of malignant appearing cells with minimal cytoplasm and dark atypical nuclei epithelial cells gland, nest, or cyst-like cells cellular origin of synovial sarcoma is unknown, but it is not the synovial cell or any cell involved in the synovium. The name SYNOVIAL sarcoma is a misnomer Immunostaining for synovial sarcoma stains positive for vimentin epithelial membrane antigen sporadic S-100 epithelial cells stain positive for keratin Treatment Operative wide surgical resection with adjuvant radiotherapy indications standard of care in most patients technique radiotherapy may be delivered either pre-surgery or post-surgery in cases of close or microscopic positive margins or larger tumors (>5cm) decreases rate of local recurrance chemotherapy Controversial data regarding chemotherapy in synovial sarcoma suggests that chemotherapy may improve both local control and overall survival Reserved for high risk tumors, advanced disease, and younger populations Prognosis Overall prognosis is poor 5 year survival is approximately 50-60% 10 year survival is approximately 25% Prognostic factors include size, grade, location, patient age, and surgical margins SYT-SSX fusion type is most important prognostic factor SYT-SSX2 better survival