Leukemia is cancer of the body’s blood-forming tissues, including the bone marrow and lymphatic system. Leukemia begins in a cell in the bone marrow, the spongy center inside of the bones where cells develop from stem cells into red cells, white cells or platelets. In leukemias, the cell mutates and becomes a type of leukemia cell classified by type of cell and by pattern of growth.
Lymphoid cells and Myeloid cells: the marrow forms myeloid cells which normally go on to form red cells. Myeloid leukemia can begin in these cells. The marrow also forms lymphocytes, the infection-fighting cells of the immune system. Lymphocytic leukemia can arise in these cells.
Acute and Chronic Leukemias: leukemias are also classified by how quickly they progress, in acute leukemia, immature white blood cells multiply rapidly in the bone marrow and are called blasts. Instead of functioning properly as the body’s infection fighters, these abnormal cells fill the blood, leaving little space for healthy cells. Acute leukemias progress rapidly without treatment. In chronic leukemia, the cancer develops more slowly, and is often diagnosed due to enlargement of the spleen.
The four main types of leukemias include:
- Acute myeloid leukemia (AML)
- Acute lymphocytic Leukemia (ALL)
- Chronic myelogenous leukemia (CML)
- Chronic lymphocytic leukemia (CLL)
Acute myeloid leukemia and acute lymphocytic leukemia-in these diseases, the acute leukemia cell multiplies to form a trillion more leukemia cells. Unlike healthy cells, these cells are called ‘nonfunctional’ because they do not function as normal and crowd out the normal cells in the marrow. With the resulting decrease in healthy red cell production, patients often experience anemia and increased bleeding and infection risks.
Chronic myeloid leukemia-the cell that begins this disease makes mature blood cells that function similar to normal cells. The number of red blood cells produced is usually less than normal, while the white blood cell count increases, which can result in severe anemia.
Chronic lymphocytic leukemia-the cell that begins this disease makes too many non- functioning lymphocytes. These cells interfere with the normal lymphocytes, causing a decrease in healthy red and white cell counts, and a weakened immune system. CLL is characterized by slow disease progression, often not requiring treatment for long periods of time.