TNF and rheumatoid arthritis: Showing a true association between TNF blockade and the development of cancer is difficult for many reasons, such as event underreporting; the risk from underlying disease (for example, patients with rheumatoid arthritis have a greater risk of developing some malignancies, such as lymphoma2-4); and the use of immunosuppressive medications (methotrexate, azathioprine, cyclophosphamide).