3) Ellman MH, Hurwitz H, Thomas C, et al. : Lymphoma developing in a patient with rheumatoid arthritis taking low dose weekly methotrexate. J Rhumatol 18: 1741-1743, 1991.
4) Harris NL and Swerdlow SH : Methotrexate-associated lymphoproliferative disorders. Pathology and genetics of tumors of hematopoietic and lymphoid tissue. World Health Organization Classification Of Tumors. pp 270-271, IARC Press, Lyon, 2001.