Acute lymphoblastic leukemia

Acute lymphoblastic leukemia is a cancer of lymphoblasts, which are immature lymphocytes, defense cells that have not finished developing. They can come from the B line or the T line, and what defines them here is that they multiply out of control.

That multiplication takes up space. The lymphoblasts progressively replace the elements of the bone marrow, the tissue inside the bones where blood is made, and other lymphoid organs as well. The blood factory is taken over by a single line of cells that never finishes maturing.

That is where the usual presentation of the disease comes from. If the marrow no longer makes everything else, red blood cells run short and anemia sets in, and platelets and neutrophils, the white blood cells that fight infection, run short too.