Primary cutaneous diffuse large B-cell lymphoma, leg type, in a patient with rheumatoid arthritis undergoing etanercept therapy.

An 84-year-old woman, who was diagnosed with rheumatoid arthritis (RA) and was treated with methotrexate and, subsequently, etanercept (ETN) for 6 years, presented with rapidly progressing painful cutaneous mass on the right medial malleolus. The patient was eventually diagnosed with primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL-LT). ETN therapy was promptly discontinued expecting spontaneous regression of the lymphoma, which was thought to have developed as other iatrogenic immunodeficiency-associated lymphoproliferative disorders. However, no tumour regression was noted. Chemoimmunotherapy was subsequently initiated, which resulted in partial remission. PCLBCL-LT rarely occurs in patients with RA. Here, we report the first case of PCLBCL-LT that developed in a patient with RA receiving ETN therapy.