Synovial Sarcoma is a malignant soft tissue tumor that arises near, but not, as the name implies, in the joint itself. About 10% of soft tissue sarcomas are synovial sarcomas.
The patient usually presents with a painful mass next to a joint which is growing in size. It usually occurs in teenagers or patients under 40 years of age, most often in the lower leg around the knee. Lower grade synovial sarcomas tend to be found on the hands or feet, and may be confused with a benign ganglion. X-rays show a soft tissue thick shadow with calcifications (deposits of calcium salts in normal bone or in soft tissue (less common)) in it. A biopsy is necessary to rule out the many other possible soft tissue masses that have calcifications but are benign. Metastases to lymph nodes are more common with synovial sarcoma than other types of soft tissue sarcomas. The tumor may also spread to the lungs in more advanced cases. Treatment consists of radical or wide excision of the tumor with adjuvant therapy (chemotherapy and/or radiation therapy). Small, low-grade tumors may do well with excision only.