Mycophenolate mofetil Active Not Recruiting Phase 2 Trials for Malignant Lymphomas / Multiple Myeloma and Plasma Cell Neoplasm / Graft Versus Host Disease (GVHD) / Leukemias / Precancerous/Nonmalignant Condition / Myelodysplastic/Myeloproliferative Diseases / Chronic Myeloproliferative Disorders / Myelodysplastic Syndromes (MDS) Treatment