Leukemia is a cancer of the early blood-forming cells. Most often, leukemia is a cancer of the 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.

A diagnosis of leukemia is usually made by analyzing a patient’s blood sample through a complete blood count (CBC) or microscopic evaluation of the blood, or by using flow cytometry. "Flow cytometry is a very sensitive technology that uses a laser beam to identify the very specific types of cells found in a sample," Dr. Siddon says.