Synovial Sarcoma, X Breakpoint 9 is a human gene encoded by the symbol, SSX9. It may also be known as: Protein SSX9. The encoded protein has an amino acid length of 188 and a mass of 21.6 kDa. Synovial Sarcoma, X Breakpoint 9 is a member of the SSX family. Homologs of this gene exist in other organisms, including: Mouse.