Inclusion Criteria:  2.Patient with histologically proven CD20+ diffuse large B-cell lymphoma (DLBCL) (WHO classification 2017) including all clinical subtypes (primary mediastinal, intravascular, etc…), with all International Prognostic Index (IPI). May also be enrolled the following malignancies:  De Novo transformed DLBCL from low grade lymphoma (Follicular, other...) and DLBCL associated with some small cell infiltration in bone marrow or lymph node. High-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements High-grade B-cell lymphoma, Not Otherwise Specified (NOS) Follicular lymphoma grade 3B 3.Positron-Emission Tomography (PET)-positive disease 4.Previously untreated high-grade B-cell lymphoma 5.Aged ≥ 80 years old at the time of signing the informed consent form (ICF) 6.Ann Arbor stage I, II, III or IV 7.Eastern Cooperative Oncology Group (ECO)G performance status ≤ 2 8.With a minimum life expectancy of 3 months 9.Male patients must practice complete abstinence or agree to use a condom during sexual contact with a pregnant female or a female of childbearing potential while participating in the study, during dose interruptions, and for 4 months following study drug discontinuation, even if they have undergone a successful vasectomy 10. Patients should be able to receive R-miniCHOP regimen (left ventricular ejection fraction > 50% and good general condition, according to investigator's judgment) 11. Patients should be able to receive adequate prophylaxis and/or therapy for thromboembolic events (aspirin or low molecular weight heparin) 12. Patient covered by any social security system (France)  Exclusion Criteria:  Any other histological type of lymphoma, Burkitt included Any history of treated or non-treated Small-B cell lymphoma prior Aggressive B Cell lymphoma diagnosis Central nervous system or meningeal involvement by lymphoma Any serious active disease (according to the investigator's decision) Poor renal function (calculated Cockcroft-Gault creatinine clearance < 30 ml/min) Poor hepatic function (total bilirubin level >30 μmol/l, transaminases >2.5 upper normal limits) unless these abnormalities are related to lymphoma Poor bone marrow reserve as defined by neutrophils <1.5 G/l or platelets <100 G/l, unless related to bone marrow infiltration by lymphoma cells (Bone Marrow Aspiration will be mandatory in case of severe cytopenias prior inclusion) Any history of cancer during the last 5 years with the exception of non-melanoma skin tumors or stage 0 (in situ) cervical carcinoma. Patients previously diagnosed with prostate cancer are eligible if (1) their disease was T1-T2a, N0, M0, with a Gleason score ≤7, and a prostate specific antigen (PSA) ≤10 ng/mL prior to initial therapy, (2) they had definitive curative therapy (i.e., prostatectomy or radiotherapy) 2 years before Day 1 of Cycle 1, and (3) at a minimum 2 years following therapy they had no clinical evidence of prostate cancer, and their PSA was undetectable if they underwent prostatectomy or <1 ng/mL if they did not undergo prostatectomy Treatment with any investigational drug within 30 days prior to prephase treatment and during the study Known HIV, active Hepatitis C Virus (HCV) infection or positive Hepatitis B Virus (HBV) test within 4 weeks before enrollment (except after hepatitis B vaccination or for patients who are HBs Ag negative, anti-HBs positive and/or anti-HBc positive but viral DNA negative) Prior treatment with anti-CD20/anti-CD19 monoclonal antibody or alemtuzumab within 3 months prior to prephase treatment Prior ≥ Grade 3 allergic reaction/hypersensitivity to thalidomide Contra-indication to highly dosed glucocorticoid (60 mg/m2/d) Neuropathy ≥ Grade 2 or painful Patient deprived of his/her liberty by a judicial or administrative decision Adult patient under legal protection