Inclusion Criteria:

- Primary mediastinal diffuse large B-cell lymphoma, CD20 positive. Patients must have
histological confirmation of the diagnosis, and in addition have a dominant mass
within the anterior mediastinum.

- No prior treatment of lymphoma. Patients may have received corticosteroids for up to
1 week for the relief of local compressive symptoms.

- Any stage of disease.

- Age at least 18 years.

- Fit to receive chemotherapy with curative intent.

- Able and willing to give informed consent, and to undergo staging including PET
scanning

- Willingness to comply with an appropriate contraceptive method in women of
childbearing potential or men.

Exclusion Criteria:

- Evidence of clinically significant cardiac disease, as defined by history of
symptomatic ventricular arrhythmias, congestive heart failure or myocardial
infarction within 12 months before study entry. Cardiac compromise due to local
extension of lymphoma will not be an exclusion criterion in the absence of other
cardiac disease.

- Impairment of bone marrow function (WBC <3.0x109/L, ANC <1.5x109/L, PLT <100x109/L),
unless due to involvement by lymphoma.

- Major impairment of renal function (serum creatinine >2x upper normal) or liver
function (ASAT/ALAT >2,5 upper normal, total bilirubin >2,5x upper normal), unless
due to lymphoma involvement.

- Known HIV infection. Patients will not be tested routinely.

- Pregnant or lactating women.

- Any psychological, familial, sociological or geographical condition potentially
hampering compliance with the study protocol and follow-up schedule; those conditions
should be discussed with the patient before registration in the trial