Phase II trial to determine the efficacy of Dose Adjusted-EPOCH-Rituximab regimen in children and adolescent with primary mediastinal large B cell lymphoma in terms of event free survival.

Inclusion Criteria:

• Histologically proven Primary Mediastinal Large B-Cell Lymphoma (PMLBL).
• PMLBL without central nervous system (CNS) involvement.
• 6 months to less than 18 years of age at the time of consent.
• Males and females of reproductive potential must agree to use an effective contraceptive method during the treatment, and after the end of treatment: during twelve months for women, taking into account the characteristics of rituximab
• Complete initial work-up within 8 days prior to treatment that allows definite staging.
• Able to comply with scheduled follow-up and with management of toxicity.
• Signed informed consent from patients and/or their parents or legal guardians

Exclusion Criteria:

• Follicular lymphoma, mucosa-associated lymphoid tissue (MALT) and nodular marginal zone
• PMLBL patients with CNS involvement
• Patients with congenital immunodeficiency, chromosomal breakage syndrome, prior organ transplantation, previous malignancy of any type, or known positive HIV serology.
• Evidence of pregnancy or lactation period.
• There will be no exclusion criteria based on organ function.
• Past or current anti-cancer treatment except corticosteroids during less than one week.
• Tumor cell negative for CD20
• Prior exposure to rituximab.
• Severe active viral infection, especially hepatitis B.
• Hepatitis B carrier status history of hepatitis B virus (HBV) or positive serology.
• Participation in another investigational drug clinical trial.
• Patients who, for any reason, are not able to comply with the national legislation.