What is Leukemia?
Leukemia is the result of the rapid overproduction of abnormal white blood cells. It affects close to 45,000 people in the United States each year.
Leukemia is the most common type of blood cancer in people older than 55. But, it’s also the most common cancer in children under 15.
What Causes Leukemia?
Leukemia occurs when abnormal white blood cells in the bone marrow quickly increase and destroy normal blood cells. This leaves a person prone to infection.
Treatment approaches for leukemia depend on the type of white blood cell affected and whether the disease is acute or chronic.
Acute leukemia forms rapidly and becomes severe quickly. Chronic leukemia grows more slowly and takes longer to advance.
Types of Leukemia
The four most common types of leukemia are:
- Acute lymphocytic leukemia
- Acute myeloid leukemia
- Chronic lymphocytic leukemia
- Chronic myeloid leukemia
Acute lymphocytic (lymphoblastic) leukemia (ALL)
ALL is more common in children.
This type of leukemia begins in the B or T lymphocytes, which are immature white blood cells. Lymphocytes are the building blocks of the lymphoid tissues that make up the immune system.
ALL can affect the bone marrow all over the body.
It can also spread to the:
- Lymph nodes
Doctors further sub-classify ALL based on the variety and developmental stage of the lymphocyte involved.
Acute myeloid leukemia (AML)
AML is the most common type of acute leukemia in adults.
It tends to progress quickly. It can affect any component of the blood and there are many subtypes of AML.
Blood stem cells in the bone marrow form into either:
- Lymphoid cells, which become white blood cells.
- Myeloid cells, which can become red blood cells, white blood cells, or platelets.
In AML, myeloid stem cells usually mature into abnormal myeloblasts, or white blood cells. But, they sometimes become abnormal red blood cells or platelets.
As they multiply, they overwhelm the normal cells in the bone marrow and blood. The cancer cells can also spread to other parts of the body.
Chronic lymphocytic leukemia (CLL)
CLL accounts for about a third of leukemia diagnoses. It usually affects older adults.
One form of CLL progresses slowly. Symptoms may not appear until years after onset. Another form of CLL grows very quickly.
CLL begins in the B lymphocytes. As the abnormal cells proliferate, they crowd out the normal cells.
More subtypes of CLL exist that affect other types of cells.
Chronic myeloid leukemia (CML)
This type of leukemia is rare. Only 10 percent of leukemias are CML.
Adults are more likely than children to get CML.
CML occurs when a genetic change turns the myeloid cells into immature cancer cells. These cells then grow slowly and overwhelm the healthy cells in the bone marrow and blood.
A subtype of CML can form very quickly. This type is hard to treat.
Hairy cell leukemia
A rare type called hairy cell leukemia (HCL) — because of how it looks under a microscope — affects fewer than 6,000 people each year.
HCL grows slowly. Some people live with the disease for many years before symptoms appear.
Prognosis — or chance of recovering from leukemia — depends on many factors.
Leukemia subtypes fall along a continuum for projected outcomes, but individual cases can deviate from these predictions.
Chromosome abnormalities and your response to treatment make a difference, as does age. People under 50 usually fare better.
A lower white blood cell count at the time of diagnosis is predictive of a better outcome.
Links to lower survival rates include a history of radiation exposure or previous chemotherapy for a different type of cancer.
Leukemia Risk Factors
Common risk factors for leukemia include:
- Benzene exposure — benzene is a carcinogen that often makes up other chemicals, such as plastics and rubbers. People who work in industries that use benzene may be at increased risk.
- Radiation exposure — people exposed to high levels of radiation (from treatment for other cancers or from nuclear weapons) are at increased risk.
- Smoking — smoking increases leukemia risk.
How is Leukemia Diagnosed?
No screening exams exist for leukemia.
Doctors often discover that a person has chronic leukemia through routine blood testing. They may also rely on their experience and current knowledge of the disease.
If your doctor suspects you may have leukemia, he or she will order specific diagnostic tests such as a:
- Blood test
- Bone marrow biopsy
- Spinal tap
Contact Us About Leukemia Care
To reach the Mario Lemieux Center for Blood Cancers at UPMC Hillman Cancer Center, call 412-864-6600.