Leukemia is a @type of blood cancer that starts in the bone marrow, where new blood cells are made. The bone marrow starts making too many blood cells that aren’t normal, called leukemia cells. These cells overtake healthy blood cells and prevent them from working like they should.
Unlike most other cancers, leukemia cells don’t always form a tumor. However, the cancer cells can spread to the bloodstream and lymph nodes. They can also travel to the brain, spinal cord and other parts of the body.