Inclusion Criteria:

- Previously untreated primary mediastinal diffuse large B-cell lymphoma, CD20
positive.

- Patients must have histological confirmation of the diagnosis (it is recommended that
the immunohistochemical panel includes: CD45, CD20, CD30, CD15, CD10, BCL6, BCL2,
MUM-1), and in addition have a dominant mass within the anterior mediastinum.

- No evidence of extranodal disease outside the chest including spleen and bone marrow.

- Age at least 18 years.

- Fit to receive chemotherapy and radiotherapy with curative intent.

- Patients will be eligible if the treatment phase consisting in a Rituximab combined
with any anthracycline-containing chemotherapy regimen without consolidation with
autologous stem cell support (e.g., 6 cycles of CHOP14-21, DA-EPOCH, Mega-CHOP or 12
weeks of VACOP-B or MACOP-B).

- At least 6 courses of Rituximab should be administered

- 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.

- Histological diagnostic material available for review.

Exclusion Criteria:

- History of malignancy other than squamous cell carcinoma, basal cell carcinoma of the
skin or carcinoma in situ of the cervix within the last 5 years.

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

- Known HIV-positive serology.

- Pregnant or lactating women.

- Any psychological, familial, sociological or geographical condition potentially
hampering compliance with the study protocol and follow-up schedule.