Leukemias are cancers that start in cells that would normally develop into different types of blood cells. Most often, leukemia starts in early forms of white blood cells, but some leukemias start in other blood cell types.
There are several types of leukemia, which are divided based mainly on whether the leukemia is acute (fast growing) or chronic (slower growing), and whether it starts in myeloid cells or lymphoid cells. Knowing the specific type of leukemia helps doctors better predict each person’s prognosis (outlook) and select the best treatment.
Acute lymphocytic leukemia (ALL) is also called acute lymphoblastic leukemia. “Acute” means that the leukemia can progress quickly, and if not treated, would probably be fatal within a few months. “Lymphocytic” means it develops from early (immature) forms of lymphocytes, a type of white blood cell.
ALL starts in the bone marrow (the soft inner part of certain bones, where new blood cells are made). Most often, the leukemia cells invade the blood fairly quickly. They can also sometimes spread to other parts of the body, including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles (in males). Some cancers can also start in these organs and then spread to the bone marrow, but these cancers are not leukemia.
*This information is from The American Cancer Society.