Hematopoietic stem-cell transplantation.

Although hematopoietic stem-cell transplantation was originally conceived more than 50 years ago as a treatment for injury from irradiation and, later, for cancer, associated problems needed to be solved before the procedure could be used clinically. Bone marrow, the source of hematopoietic stem cells, is not a solid organ but is rather diffuse and not directly accessible. Furthermore, hematologic cells can initiate immune reactions that may thwart transplantation. Hematopoietic stem-cell transplantation is used primarily for hematologic and lymphoid cancers but also for many other disorders (Table 1). In this review, I summarize background information about hematopoietic stem-cell transplantation and discuss the role of the procedure in treating malignant and nonmalignant conditions, focusing on recent progress.