Leukemia is a cancer that affects the body's early blood-forming cells, states the American Cancer Society. This includes the bone marrow, where blood cells are made, and the lymphatic system.
Leukemia most often occurs in white blood cells, but it can start in other types of blood cells. People with leukemia have bone marrow that makes numerous abnormal white blood cells. These blood cells grow faster than normal cells and grow uncontrollably. As the cancer progresses, the normal blood cells are crowded out, leading to anemia, bleeding and infections. Leukemia cells can spread to the lymph nodes or other organs, adds WebMD.
The exact causes of leukemia are unknown, states Mayo Clinic. A combination of environmental and genetic factors, such as inherited DNA mutations, can contribute to the development of leukemia. Risk factors include exposure to high levels of radiation; having a family history of leukemia; certain blood disorders, such as myelodysplastic syndromes; and a history of previous cancer treatment. Leukemia is diagnosed by doing a physical exam to look for signs of anemia and swollen lymph nodes; examining blood samples for abnormal levels of white blood cells; and examining bone marrow samples. Additional tests are performed to determine the stage of cancer and how far it has spread in the body.