We report on a 74-year-old female patient with a primary cutaneous CD20+, diffuse large cell B-cell lymphoma of the lower leg resembling a chronic non-healing leg ulcer. There was no evidence of systemic involvement on computed tomography (CT) scans of the chest, abdomen and pelvis; a slightly enlarged lymph node in the right groin showed dermatopathic lymphadenopathy on histology and immunohistochemistry. Involvement of the bone marrow and peripheral blood was ruled out by punch biopsy and fluorescent activated cell sorter (FACS) analysis of the blood, respectively. Therapeutic anti-CD20 monoclonal antibody rituximab was given at 375 mg m(-2) i.v. once weekly for 7 weeks, without adverse effects, resulting in a minor improvement in the centre of the ulcerated tumour. Unfortunately, the response was not maintained, and after 7 weeks of treatment the patient started to develop new tumour lesions at the border of the ulcer. Local radiotherapy was started and combined photon and electron beam irradiation induced complete remission of the B-cell lymphoma.