Lenalidomide and Dexamethasone for Rosai-Dorfman Disease

Inclusion Criteria: * Histologically confirmed diagnosis of RDD * Age ≥18 years * Eastern Cooperative Oncology Group (ECOG) performance status 0-2. * Patients must have adequate renal, liver, and bone marrow function as defined by the following criteria: Absolute neutrophil count ≥1500 cells per mm3 Platelet count ≥100000 cells per mm3 Creatinine clearance \[according to Cockcroft formula\] ≥60 mL/min. Aspartate aminotransferase and alanine aminotransferase ≤2·5×upper limit of normal \[ULN\], and total bilirubin ≤2·5×ULN; or ≤10×ULN in the case of known liver involvement by RDD. * No active or untreated infection. * No cardiac abnormalities. * Subject provide written informed consent. * A female is eligible to enter and participate in this study if she is of: Non-childbearing potential including ω Any female who has had a surgical procedure rendering her incapable of becoming pregnant. ω Subjects have experienced total cessation of menses for more than 1 year and be greater than 45 years in age. ⎫ Childbearing potential, including any female who has had a negative serum pregnancy test within 2 weeks prior to the first dose of study treatment, and agrees to use adequate contraception. • Male subjects must use an effective barrier method of contraception during the study and for 90 days following the last course of MA if sexually active with a childbearing potential Exclusion Criteria: * Patients had concurrent malignancies. * History of myocardial infarction, or unstable angina, or New York Heart Association (NYHA) Grade III-IV within 6 months prior to Day 1. * Women who were pregnant or of childbearing potential. * Known HIV seropositive, active hepatitis C infection, and/or hepatitis B (defined as HCV RNA≥1000 copies or HBV DNA ≥1000 copies at screening). * Major surgical procedure within 28 days prior to the first dose of study treatment. * Presence of uncontrolled infection. * Evidence of active bleeding or bleeding diathesis. * Any serious and/or unstable pre-existing medical, psychiatric, or other condition that could interfere with subject's safety, provision of informed consent, or compliance to study procedures.