Types of Leukemia

A blood sample viewed under a microscope shows leukemia cells (in purple). Washington University has received funding to continue... A blood sample viewed under a microscope shows leukemia cells (in purple). Washington University has received funding to continue cutting-edge research into better therapies for various types of leukemia. GETTY IMAGES

Leukemia develops in special stem cells located in the bone marrow. These stem cells create all of the blood cells in the body. In cases of leukemia, the stem cells stop producing healthy blood cells and instead produce immature cells that fail to function as they should. Leukemia most often occurs in the stem cells that form white blood cells.

There are two basic categories of white blood cells: myeloid cells and lymphoid cells.

If you have leukemia, your physicians will determine whether it is affecting myeloid cells or lymphoid cells, and whether it is slow or fast-growing. They will then assign it a type and plan your treatment accordingly.

What are the different types of leukemia?

There are four main types of leukemia. Acute leukemias are fast-growing, while chronic leukemias are slow-growing. The four types are:

  • Acute lymphoblastic leukemia
  • Acute myeloid leukemia
  • Chronic lymphoblastic leukemia
  • Chronic myeloid leukemia

What is acute lymphoblastic leukemia?

Acute lymphoblastic leukemia, or ALL, is an aggressive form of leukemia that occurs in lymphoid cells. Lymphoid cells develop into lymphocytes, which are white blood cells that protect the body from invading germs. In cases of ALL, malignant, immature lymphoid cells, known as lymphoblasts, proliferate rapidly in the bone marrow and bloodstream.

What is acute myeloid leukemia?

Acute myeloid leukemia, or AML, arises in myeloid cells. These cells develop into white blood cells called granulocytes and monocytes. When you have acute myeloid leukemia, immature myeloid cells, or myeloblasts, start to multiply in your bone marrow and blood. The myeloblasts quickly overwhelm normal, healthy cells. AML is an aggressive disease.

What is chronic lymphocytic leukemia?

Chronic lymphocytic leukemia, or CLL, differs from ALL in that the cancer is more slow-growing. The cancerous cells are more mature, and can still function somewhat normally in the body. This means that it takes longer for them to cause problems.

CLL is the most common type of leukemia to develop in adult patients. It almost always occurs in older populations – patients are, on average, 72 years old at the time of diagnosis. Because the disease is slow-moving, physicians frequently wait to treat it until it causes symptoms.

What is chronic myeloid leukemia?

 Chronic myeloid leukemia, or CML, occurs when the body produces abnormal myeloid cells that are more developed than the myeloblasts found in AML but too immature to support the body as they should. Most people with CML have a gene mutation called the Philadelphia chromosome, a mutation that occurs spontaneously and is not passed from parent to child. It tends to arise in older populations.

CML progresses gradually. Patients often don’t need traditional chemotherapy, and are instead treated with special drugs that target the Philadelphia chromosome.