Paraneoplastic symptoms, caused by a malignancy, but not directly related to invasion by the tumor or its metastases are the result of a wide variety of tumor-derived biologic mediators like hormones, peptides, antibodies, cytotoxic lymphocytes, autocrine and paracrine mediators. Recognition of paraneoplastic syndromes is important, as it may lead to an early diagnosis of cancer. There is some evidence that systemic inflammatory diseases, such as rheumatoid arthritis (RA), lupus, scleroderma or dermatomyositis may increase the risk for the development of malignancies, predominantly lymphoproliferative disorders. However, reports are somewhat controversial. Immunosuppressive and cytotoxic drugs used in antirheumatic therapy, such as methotrexate, cyclophosphamide, azathioprine or anti-TNF biologicals may also lead to the development of such tumors. Tumor-associated antigens may be produced by inflammatory cells and their production may be increased in RA and other autoimmune diseases.