Background. Large B-cell lymphoma of the leg in elderly subjects, of intermediate prognosis according to the new EORTC classification, may present as nodular or ulcerated forms. There has been relatively little study of the various etiological hypotheses advanced, including venous insufficiency. We report the case of an elderly man with chronic leg ulcer, recently undergoing modification, in which microscopy revealed large B-cell lymphoma (CD20-). Patients and methods. A 78 year-old man presented chronic ulcer of the right leg of mixed origin with severe venous insufficiency and arteritis. In the previous 2 months, 2 nodules appeared in the centre of the ulcer. Histological examination of a skin biopsy revealed the presence of large B-cell lymphoma and immunohistochemical analysis showed positive anti-CD79a+, CD20- antibody labeling of cells. Staging studies showed only locoregional invasion. Because of the positive CD20- labeling, ZEM chemotherapy (idarubicine, cyclophosphamide, prednisolone) was given, resulting in disappearance of the nodules after four months and preliminary epidermal healing of the ulcer. Several months later, severe infectious complications necessitated amputation. Examination of the excised sample showed no residual tumor. Discussion. Many causal links have been proposed between large B-cell lymphoma of the leg and aetiologies such as infectious agents, Koebner phenomenon and chronic lymphedema, as well as various other vascular factors. A number of hypotheses were proposed in the present case. It may have been leg ulcer cutaneous B-cell lymphoma, or, more likely, development of lymphoma on a chronic mixed ulcer, with the respective roles of vascular disease, local immunosuppression and antigenic stimulation subject to debate.