Stem cell transplantations are done to treat some forms of cancer and sometimes to treat other rare diseases. Today, leukaemia is the most common disease where blood stem cells are often used as a last resort. There are many other diseases that can be treated in the same way, including severe anaemia, immunodeficiency diseases and metabolic disease. In addition to leukaemia, cancers treated with stem cell transplantation include e.g. lymphoma and myeloma. Currently, a stem cell transplantation can be potentially lifesaving for around 70 different diseases.