Hematology is the study of blood in health and disease. It includes problems with the red blood cells, white blood cells, platelets, blood vessels, bone marrow, lymph nodes, spleen, and the proteins involved in bleeding and clotting (hemostasis and thrombosis). A hematologist is a medical doctor who applies this specialized knowledge to treat patients with blood conditions.

A hematologist-oncologist is a physician who specializes in the diagnosis, treatment and/or prevention of blood diseases and cancers such as iron-deficiency anemia, hemophilia, sickle-cell disease, leukemia and lymphoma. This physician is trained in Hematology — the study of blood — and Oncology — the study of cancer.

A bone marrow transplant is a medical procedure performed to replace bone marrow that has been damaged or destroyed by disease, infection, or chemotherapy. This procedure involves transplanting blood stem cells, which travel to the bone marrow where they produce new blood cells and promote growth of new marrow.