 Swelling may be due to many causes, including infections, tumors, autoimmune disease, drug reactions, diseases such as amyloidosis and sarcoidosis, or because of lymphoma or leukemia.Depending on the cause, swelling may be painful, particularly if the expansion is rapid and due to an infection or inflammation.Lymph node enlargement may be localised to an area, which might suggest a local source of infection or a tumour in that area that has spread to the lymph node.