Has had a prior stem cell or bone marrow transplant. Allogeneic stem cell transplant patients and any patient who has relapsed within 100 days of stem cell infusion following an autologous bone marrow transplant. ELIGIBILITY CRITERIA FOR BONE MARROW TRANSPLANT EXCLUSION CRITERIA FOR BONE MARROW TRANSPLANT Bone marrow transplant: patient must be:\r\n* >= 6 months since allogeneic bone marrow transplant prior to registration\r\n* >= 3 months since autologous bone marrow/stem cell prior to registration Autologous or allogeneic stem cell or bone marrow transplant within 3 months prior to cycle 1 day 1 History of bone marrow transplant and stem cell rescue Patient must be >= 12 weeks since autologous bone marrow/stem cell transplant prior to enrollment INCLUSION CRITERIA FOR STRATUM C: Patient must be:\r\n* >= 12 weeks since autologous bone marrow/stem cell transplant prior to enrollment\r\n* >= 5 years since allogeneic bone marrow transplant prior to enrollment with no evidence of active graft versus (vs.) host disease Previous bone marrow or stem cell transplant Bone marrow transplant or stem cell rescue Prior allogeneic bone marrow- or stem cell-transplant Prior autologous bone marrow or peripheral blood stem cell transplantation =< 100 days prior to registration or if recovery from the transplant is inadequate Prior bone marrow or stem cell transplant Prior stem cell or bone marrow transplant Prior allogeneic bone marrow/peripheral blood stem cell transplant Back-up autologous stem cells harvested from bone marrow >= 3 months prior to registration for autologous bone marrow/stem cell transplant History of organ allograft (allogeneic bone marrow or stem cell transplant) within 4 months prior to first dose of study drug Prior bone marrow or stem cell transplant. History of organ allograft (except for corneal transplant) or autologous or allogeneic bone marrow transplant, or stem cell rescue within 3 months prior to the first dose of IMP Subject has undergone a bone marrow transplant Previous bone marrow or stem cell transplant Prior allogeneic bone marrow or stem cell transplant Prior autologous bone marrow or stem cell transplant within 1 year of enrollment Prior allogeneic bone marrow or stem cell transplant Prior autologous bone marrow or stem cell transplant or prior radiation therapy (RT) > 20 Gy to a critical organ within 1 year of enrollment Autologous bone marrow transplant or stem cell rescue within four months of start of study drug History of bone marrow transplant; Prior bone marrow or stem cell transplant Prior autologous or allogeneic bone marrow or stem cell transplant Participant is a candidate for a bone marrow or stem cell transplant within 12 weeks after study enrollment. Relapsed and or refractory multiple myeloma after at least one prior line of therapy; there is no upper limit of prior lines of therapy; patients who are ineligible for stem cell transplantation are allowed; patients should have received at least one prior novel agent (immunomodulatory agents or proteasome inhibitors); patients eligible for bone marrow transplant must have undergone bone marrow transplant (BMT) prior to enrollment Post autologous stem cell transplant bone marrow biopsy core that is consistent with morphologic remission Prior autologous or allogeneic bone marrow/peripheral blood stem cell transplant Patients with a history of bone marrow transplant within the previous two years The patient had a previous bone marrow or stem cell transplant 18F FLT CANDIDATE TRANSPLANT RECIPIENT: Donor who is willing to undergo bone marrow or stem cell harvest Patients with a history of bone marrow transplant within the previous two years History of allogeneic bone marrow/stem cell transplant Not eligible for stem cell/bone marrow transplant or have refused stem cell/bone marrow transplant or have relapsed after autologous or allogeneic stem cell/bone marrow transplant Has had a prior stem cell or bone marrow transplant Autologous bone marrow transplant or stem cell rescue within 4 months of study entry Prior autologous bone marrow or peripheral blood stem cell support within 1 year Patient has participated or is currently participating in any bone marrow derived autologous and allogeneic stem cell or gene therapy study. Prior bone marrow transplant Prior bone marrow or stem cell transplant; Autologous or allogeneic stem cell or bone marrow transplant within 3 months prior to first dose of study drug. Recent bone marrow transplant Autologous or allogeneic stem cell or bone marrow transplant within 3 months prior to first dose of study treatment. Autologous bone marrow transplant or stem cell rescue within 4 months of study entry History of organ allograft (except for corneal transplant) or autologous or allogeneic bone marrow transplant, or stem cell rescue within 3 months prior to the first dose of study drug. Patients with a history of bone marrow transplant within the previous two years Patients eligible for bone marrow transplant, regardless of age Prior autologous bone marrow or peripheral stem cell transplant less than 3 months prior to enrollment. All patients must be enrolled within 48 hours of admission except patients in the bone marrow transplant arm who may be enrolled at the beginning or during their bone marrow transplant Patients receiving myeloablative chemotherapy in preparation for allogeneic or autologous bone marrow or stem cell transplant Participants or their parents must consent to participation in active bone marrow and peripheral blood stem cell transplant protocols at the National Institutes of Health (NIH) Allogenic bone marrow transplant or stem cell rescue within 4 months before first dose of study drug; patients must have completed immunosuppressive therapy before enrollment Patients with DLBCL: Cancer progression after transplant, or be unwilling, unable or not an appropriate candidate for an autologous stem cell or bone marrow transplant Bone marrow transplant recipients. Previous bone marrow transplant Admission to the University of North Carolina (UNC) Hospital Bone Marrow Transplant Unit for allogeneic stem cell transplant History of bone marrow transplant Recipient of a stem cell or bone marrow transplant.