Types of Leukemia

April 19, 2024 
This page was reviewed under our medical and editorial policy by Guido Marcucci, M.D., Chair, Department of Hematologic Malignancies Translational Science, City of Hope Duarte

Leukemia is the term given to cancers of the blood cells. There are different types of leukemia, which are determined by such factors as how quickly the abnormal cells grow and the type of blood cell that is impacted. With leukemia, blood cells that don’t function properly multiply and don’t do what they are supposed to do. The abnormal cells may also take up too much space in the bone marrow, making it harder for the healthy cells to have enough room to do their jobs.

Leukemia is classified as either acute (fast growing) or chronic (slow growing).

Leukemia is also classified according to the blood cell type that becomes abnormal and multiplies:

• Lymphocytic leukemias start in white blood cells in the bone marrow called lymphocytes.
• Myeloid (or myelogenous) leukemias start in myeloid (blood-forming) stem cells of the bone marrow. These cells normally mature into healthy white blood cells, red blood cells or platelets.

Leukemia most often causes the bone marrow to produce too many abnormal white blood cells that don’t function the way healthy cells do to fight infection. But sometimes other types of cells, such as red blood cells and platelets, are affected and undergo changes as well.

Differentiating Leukemia Types

Lymphocytic leukemias begin in lymphoid stem cells that will become lymphocytes, a type of white blood cell. The lymphocyte’s job is to orchestrate the immune system response to foreign invaders, disease or infection. The abnormal cells multiply and may move from the bone marrow into the blood and other organs.

Myeloid leukemias begin in myeloid cells that turn into white or red blood cells or platelets, but most often affect the cells that turn into white blood cells. The myeloid cells affected are called granulocytes and monocytes, and both affect how the immune system works. The abnormal cells multiply and may move to the bloodstream and other areas of the body.

Both types of leukemia may be acute or chronic, and they may progress rapidly or slowly.

In acute forms of leukemia, the cells affected are immature cells called blasts. These early cells multiply quickly and don’t have a lot of normal function. The disease progresses rapidly and requires immediate treatment.

In chronic forms of leukemia, the cells affected are more mature blood cells that have a bit more function than early, immature cells. These cells divide and multiply slowly and have some normal function that diminishes over time. Symptoms are less noticeable compared to the acute forms of leukemia.

People may often live for many years with chronic leukemias. However, chronic leukemias are harder to treat than acute leukemias.

Chronic Leukemia Types

The three main types of chronic leukemia are:

• Chronic lymphocytic leukemia (CLL)
• Chronic myeloid leukemia (CML)
• Chronic myelomonocytic leukemia (CMML)

Chronic lymphocytic leukemia is one of the most common forms of leukemia, accounting for one-third of all leukemias. It most often affects adults in their 60s and 70s. With CLL, some lymphocytic cells mature partly, but not all the way. The cells may look normal, but they are unable to do their job as well as healthy lymphocytic cells. Patients may have CLL for several years before they experience any symptoms and require treatment. Eventually, the cancer may spread to the blood and may affect the lymph nodes, as well as the liver, spleen and other organs. Eventually, the patient’s bone marrow may be unable to function.

Chronic myeloid leukemia, also called chronic myelogenous leukemia, starts in the myeloid cells of the bone marrow. Like CLL, it is a slow-growing cancer. Patients may have CML for some time before they experience symptoms. Eventually, CML may spread to the bloodstream and then to other parts of the body, including the spleen.

Chronic myelomonocytic leukemia is most often found in older adults. Patients with CMML often have an enlarged spleen and/or liver. They also have too many monocytes, a type of white blood cell, and too few of some other blood cell types. In up to a third of patients, it may progress to acute myeloid leukemia (AML).

Acute Leukemia Types

Two of the most common types of acute leukemia are:

• Acute lymphocytic leukemia (ALL)
• Acute myeloid leukemia (AML)

Acute lymphocytic leukemia is also known as acute lymphoblastic leukemia. It is more common in children than adults and may worsen quickly if left untreated. This type of acute leukemia starts when the bone marrow makes too many lymphocytes, the cells that support lymph tissue, such as the lymph nodes and spleen. Normally, lymphocytes help fight infection, but with this condition they crowd out healthy cells, leading to infection, bleeding easily and anemia.

Acute myeloid leukemia has several names, including acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia and acute non-lymphocytic leukemia. AML is mostly diagnosed in older people, but it may also affect children. AML starts in the bone marrow and moves quickly into the blood. From there, it may spread to the lymph nodes, liver, spleen, testicles, brain and spinal cord.

Rare Types of Leukemia

Some types of leukemia are less common. These include:

• T-cell prolymphocytic leukemia (T-PLL)
• Large granular lymphocytic leukemia (LGL)
• Hairy cell leukemia

T-cell prolymphocytic leukemia. T-cells are white blood cells that protect the body from infection. A rare cancer, T-cell prolymphocytic leukemia occurs when mature T-cells grow out of control. T-PLL is mostly diagnosed in adults in their early 60s. More men than women develop T-PLL, which is fairly aggressive. T-PLL has also been found in some older children and younger adults.

Large granular lymphocytic leukemia. This rare, chronic leukemia also affects a type of white blood cell called lymphocytes, part of the body’s immune system. People with LGL have enlarged lymphocytes that contain granules. These may be seen when blood samples are examined under a microscope.

Hairy cell leukemia. This is a rare type of chronic leukemia that begins in the bone marrow. Its name comes from the short, hair-like projections seen on blood cells. The cells replicate quickly, crowding out normal, healthy white blood cells, red blood cells and platelets.