The purpose of this study is to evaluate absence of proven, probable, possible, suspected invasive fungal disease (IFDs) through the end of prophylaxis therapy and during 4 weeks after stopping of micafungin prophylaxis after allogeneic hematopoietic stem cell transplantation in pediatric and adolescent neutropenia patients. Patients will receive micafungin until the earliest of the following: 1) neutrophil engraftment; 2) development of proven, provable, possible or suspected invasive fungal disease; 3) development of unacceptable drug toxicity; 4) withdrawal from study participation or discontinuation of study treatment. Safety profile of micafungin is also evaluated.