Other iatrogenic immunodeficiency-associated lymphoproliferative disorders (OIIA-LPD) comprise lymphoid proliferations or lymphomas that arise in patients treated with immunosuppressive drugs for autoimmune diseases, especially rheumatoid arthritis (RA) treated with methotrexate (MTX). MTX has been increasingly administered to patients with RA, resulting in methotrexate-associated lymphoproliferative disorder (MTX-LPD) in patients. We report herein on four cases of patients with RA, who diagnosed with head and neck region. In two cases (one case MTX and another case tacrolimus) drug therapy was discontinued, when the patients were diagnosed as having OIIA-LPD in only a few local findings. These patients have followed good clinical courses for 24 months. In the other two cases, consultations were performed for cervical lymphadenopathy by the Division of Rheumatology. In one case drug therapy was discontinued and a good clinical course was followed. In case of the other patient, however, who had undergone tacrolimus therapy after MTX therapy was discontinued, she relapsed and died. In the case of patients with an autoimmune disease such as RA who are taking MTX, tacrolimus, or anti TNF-α therapy, when cervical lymphadenopathy and extranodal disease are detected, OIIA-LPD should be suspected. We should cooperate with a hematologist-oncologist, a rheumatologist, and pathologist in such a case.