Leukemia is a type of cancer that affects the blood and bone marrow. It begins in the immature or early forms of blood cells, specifically in the bone marrow, which is the soft, spongy tissue inside bones where blood cells are produced. In leukemia, abnormal blood cells are produced in large quantities and do not mature properly. These abnormal cells, called leukemia cells or blasts, crowd out healthy blood cells in the bone marrow, leading to problems with normal blood cell production. read more