In addition, elevated serum levels of FSTL1 were detected in patients with rheumatoid arthritis, and Sjögren’s syndrome (SS), levels which are much higher than the levels observed in other chronic inflammatory diseases such as ulcerative colitis, systemic lupus erythematosus, systemic sclerosis, and polymyositis/dermatomyositis which, however, show altered levels of FSTL1 [17]. Here, FSTL1 is linked to synovial sarcoma.