During drug administration and leukapheresis, patients will be hospitalized at George Papanicolaou Hospital in Thessaloniki, Greece. Patients who failed to mobilize in the previous protocol will receive Mozobil and G-CSF and will be hospitalized for 5-8 days for the duration of drug administration and leukapheresis. They will receive G-CSF for several days; Mozobil will be added on the last few days of G-CSF. New patients will receive Mozobil only and will be hospitalized for 2-3 days for drug administration and leukapheresis. Mozobil is administered at 240µg/kg, under the skin. Participants will undergo two or three leukapheresis procedures in a row if low numbers of blood stem cells were recovered in the first (and possibly second) leukapheresis. Participants will be discharged from the hospital the day following the last leukapheresis procedure. Weekly follow-up visits will occur for the next month, either at G. Papanicolaou Hospital, or at the participant's local doctor's office. The total period of study participation is approximately 5 weeks. In the event that Mozobil alone does not cause mobilization of high levels of blood cells, patients will be invited to repeat the protocol three months later, receiving Mozobil and G-CSF.