How does Leukemia start?

How leukemia begins depends in part on the type of leukemia present. All cancers involve an abnormal cell in the body which begins to multiple rapidly, crowding out the normal cells with immature cancerous cells. With leukemia, this abnormal cell growth is specific to bone marrow cells, but can differ a little as to which type. In lymphocytic leukemia, the bone marrow cells that are supposed to form the lymphocytes, a type of white blood cell, are affected. In myelogenous leukemia, the bone marrow cells responsible for forming the red blood cells, platelets, and certain other types of white blood cells are affected. Basically, leukemia starts when abnormal cells in the bone marrow start to proliferate.