Lenalidomide in Relapsed or Refractory Primary-cutaneous Large B-cell Lymphoma Leg-type : Multicentre Prospective Phase II Single Arm Trial of the French Study Group of Cutaneous Lymphoma

Inclusion Criteria: * Biopsy-proven Primary cutaneous large B-cell lymphoma leg-type * Clinically measurable skin involvement (T1-T3) or skin and nodal (N1-N3) involvement measurable by PET-CT, corresponding to : Relapse after initial complete response (CR) after R-polychemotherapy Or Partial response or stable disease after R-polychemotherapy * Age \> 18 years * Life expectancy \> 3 months * WHO performance status 0-2 * Skin biopsy performed at the inclusion on a skin tumor : new tumor in case of relapsing PCLBCL-LT or initial skin tumor refractory to the previous treatment * Signed informed consent for clinical and biological analyses. The Lenalidomide Information Sheet will be given to each patient receiving lenalidomide study therapy. The patient must read this document prior to starting lenalidomide study treatment and each time they receive a new supply of study drug. * Social security cover * Conditions of global RPP have to be fulfilled by all the patients * The Lenalidomide Education and Counseling Guidance Document must be completed and signed by either a trained counselor or the Investigator at the participating clinical center prior to each dispensing of lenalidomide study treatment. A copy of this document must be maintained in the patient records. Exclusion Criteria: * Central nervous system involvement (cerebral CT scan is performed at the inclusion) * One or more of the biological abnormalities : Neutrophil count \< 1,500/mm3 ; Platelet count \< 60,000/mm3 ; Transaminases \> 5 x upper limit of normal ; Total bilirubin \> 2.0 mg/dl (34 µmol/L)/ conjugated bilirubin\>0.8 mg/dL, except of haemolytic anemia ; Creatinine clearance \< 50 mL /min ( measured or calculated according to the method of Cockcroft-Gault) * Pregnant or lactating females, potentially childbearing females defined by sexually mature female who: 1) has not undergone a hysterectomy (the surgical removal of the uterus) or bilateral oophorectomy (the surgical removal of both ovaries) or 2) has not been naturally postmenopausal (amenorrhea following cancer therapy does not rule out childbearing potential) for at least 24 consecutive months (i.e., has had menses at any time during the preceding 24 consecutive months. * Patients should not receive steroids continuously except for prednisone for tumoral flare treatment * Uncontrolled infectious and thromboembolic diseases * Subjects not willing to take deep venous thrombosis prophylaxis * Prior history of malignancies unless the subject has been free of the disease for ≥5 years. Exceptions include basal cell skin carcinoma, carcinoma in situ of the cervix or of the breast * Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form * Known seropositive for or active viral infection with HIV, Hepatitis B and C virus. * Uncontrolled intercurrent illness including, but not limited to ongoing or active infection requiring parenteral antibiotics, uncontrolled diabetes mellitus as defined by the investigator * Chronic symptomatic congestive heart failure (III or IV of the NYHA Classification for Heart Disease) * Unstable angina pectoris, angioplasty or myocardial infarctions within 6 months * Clinically significant cardiac arrhythmia that is symptomatic or requires treatment, or asymptomatic sustained ventricular tachycardia. * Prior ≥ Grade 3 allergic reaction/hypersensitivity or desquamative rash while taking thalidomide * Any standard or experimental anti-cancer drug therapy or radiation within 3 weeks of the initiation of study drug therapy. * Participation in another clinical trial