All patients will be recruited approximately 1 month before transplantation (before pre-transplant conditioning chemotherapy and pre-surgery evaluation) and followed-up to 1 year post-transplantation. Thus, each subject will be followed-up for a 13-month period. At entry, a questionnaire will document socio-demographic data and pre-transplant clinical indicators such as age, gender, primary diagnosis, previous chemotherapy, previous transfusion, etc. During follow-up, case report forms (CRF) will allow prospective reporting of all variables pertaining to EBV serology, transplantation, blood product transfusion and EBV complication.