What is leukemia?

Leukemia is a blood cancer that begins when the body’s white blood cells change and grow out of control.

Our blood has three types of cells: white blood cells (to fight infection), red blood cells (to carry oxygen) and platelets (to help blood clot). Every day, a healthy body makes millions of new blood cells in the bone marrow (the soft, spongy tissue that fills the center of bones).

With leukemia, the white blood cells grow out of control. They crowd out the red blood cells and platelets your body needs to be healthy. Eventually, there aren’t enough red blood cells to supply oxygen, enough platelets to clot the blood, or enough normal white blood cells to fight infection. This can hurt the way the major organs work and cause other problems, such as infection, anemia, bruising, and bleeding.

More information about leukemia (National Cancer Institute).

What leukemia is not

It’s important to know that leukemia is different from lymphoma. Although both are blood cancers and their names sound similar, each cancer starts in a different type of cell.

Leukemia starts in blood-forming cells inside bone marrow, while lymphoma starts in infection-fighting lymphocytes.

Types of leukemia

Leukemia can be described in two ways: acute (grows quickly) or chronic (grows slowly over time). It is also categorized by which kind of white blood cells are involved (lymphocytes or myeloid cells).

The four main types of leukemia include:

  • Acute myeloid (or myelogenous) leukemia (AML)
  • Chronic myeloid (or myelogenous) leukemia (CML)
  • Acute lymphocytic (or lymphoblastic) leukemia (ALL)
  • Chronic lymphocytic leukemia (CLL)

Your symptoms and treatment will vary depending on what type of leukemia you have. Your doctor will help you understand which kind of leukemia you have and the best treatment options for you.