• Also Known As:
  • Acute Lymphocytic Leukemia (ALL)
  • Chronic Lymphocytic Leukemia (CLL)
  • Acute Myeloid Leukemia (AML)
  • Chronic Myeloid (myelogenous) Leukemia (CML)
  • Acute Promyelocytic Leukemia (APL)
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What is leukemia?

Leukemia is cancer of the blood and bone marrow. Bone marrow, located in the spongy portions of the body’s bones (primarily ribs, vertebrae, sternum, bones of pelvis), makes early blood-forming cells, precursors of red blood cells, platelets, and white blood cells. These immature blood cell precursors grow and mature in the bone marrow until being released into the bloodstream.

Leukemia develops when bone marrow forms abnormal blood cells that divide out of control. Most often, leukemia pertains to white blood cells, but it can occur in other types of bloods cells too. Normal white blood cells are the body’s infection fighters but in leukemia, the abnormal white blood cells, called leukemia cells, don’t die at the same rate as normal blood cells. Instead, they accumulate and crowd out normal cells, including red blood cells, platelets, and normal white blood cells and their precursors, in the bone marrow. This can lead to difficulty getting enough oxygen to tissues (anemia), easy bruising and bleeding, and increased risk of infections.

Over time, leukemia cells can spread through the bone marrow and bloodstream (so-called “liquid tumor”), where they continue to divide, sometimes forming solid tumors and damaging organs. The organs affected depend on the type of leukemia. For example, the spleen, liver, and lymph nodes may become enlarged and swollen with the abnormal cells. Sometimes, leukemia cells reach the central nervous system (the brain and spinal cord) and build up in the cerebrospinal fluid.

In the United States, more than 48,000 people are diagnosed each year with leukemia and more than 23,000 die of the disease. Leukemia most often occurs in adults older than age 55, but it is the most common type of cancer in children and teens younger than 15 years old.

The cause of most leukemias is not known. Exposure to radiation, cancer-causing chemicals like benzene, and some anticancer drugs have been shown to increase the risk of developing leukemia. Some cases are associated with genetic disorders or rare viral infections.


About Leukemia


There are multiple types of leukemia. Each leukemia is classified based on whether it grows quickly and is rapidly lethal if not treated (acute) or grows slowly (chronic) and the type of white blood cell in which the cancer started.

Two categories of early blood-forming cells (immature precursors) produce white blood cells:

  • Myeloid precursor cells produce red blood cells, platelets, and several white blood cells types, known as granulocytes. Granulocytes circulate in the blood and fight infections by killing and digesting bacteria.
  • Lymphoid precursor cells develop into lymphocytes, another type of white blood cell that is found in both the blood and the lymphatic system. They coordinate the body’s immune response and a subset of lymphocytes produce antibodies.

Accordingly, leukemia can be classified as myeloid or lymphoid.

(Other types of cancer affect lymphocytes but occur in the lymphatic system, not the bone marrow. These are called lymphomas and are diagnosed and treated differently. They are discussed in the Lymphoma article.)

There are four main categories of leukemia:

  • Acute lymphocytic leukemia (ALL). This type develops from immature lymphocytes. The lymphoid leukemia cells in ALL are called leukemic lymphoblasts. ALL can grow and spread quickly and, without treatment, could be fatal within a few months. Leukemic blast cells build up in the bone marrow and blood. The cancer can sometimes spread to the lymph nodes and central nervous system. One ALL form is caused by pieces from two chromosomes breaking off and switching places (translocation). This results in an altered, fused gene (called BCR/ABL1) on chromosome 22 (also known as the Philadelphia chromosome). This altered gene makes an abnormally functional protein that leads to the overproduction of immature lymphoid cells. This form is called Philadelphia chromosome-positive ALL. Untreated ALL can lead to anemia, poor immunity, and easy bleeding and bruising. ALL is more common in children than adults.
  • Chronic lymphocytic leukemia (CLL). This type also begins in immature lymphocytes, but the appearance of leukemic cells resembles mature lymphocytes. It progresses more slowly compared with some other types of leukemia. The slow-growing form of CLL can remain stable for years and does not require treatment. However, there is a faster-growing form of CLL that blocks normal blood cell production and requires treatment. People with CLL may have enlarged lymph nodes (called lymphadenopathy), immunoglobulin deficiencies that lead to poor immunity, autoimmunity (such as autoimmune hemolysis), and an enlarged spleen. CLL mainly affects older adults.
  • Acute myeloid leukemia (AML). This is generally a rapidly developing cancer where immature myeloid cells continually divide in the bone marrow or other tissue and can replace bone marrow with immature, dysfunctional white blood cells. Untreated AML leads to anemia, poor immunity and infections, and very easy bruising and bleeding. It is most common in older adults but can also occur in children and young adults. There are several subtypes of AML. As an example, acute promyelocytic leukemia (APL) is a subtype of AML that is treated differently than other types of AML and tends to have a better outcome.
  • Chronic myeloid (myelogenous) leukemia (CML). This is a slow-growing type. People with CML often have no symptoms at first and are often diagnosed during a routine blood test or physical. When symptoms do appear, they are similar to common, less serious illness and include low energy, pale skin, stomach discomfort caused by an enlarged spleen, and unexplained weight loss. Like ALL with BCR/ABL1 (see above), CML is caused by the abnormal BCR/ABL gene on chromosome 22, the Philadelphia chromosome. Left untreated, CML leads to anemia, poor immunity, excessive bruising and bleeding, and markedly enlarged spleen. CML usually occurs in adults, with people 65 and over at greater risk. It rarely affects children. CML generally can be effectively treated with drugs called tyrosine kinase inhibitors.

Signs and Symptoms

Signs and symptoms of leukemia vary depending on the kind of leukemia.

Acute leukemia may cause signs and symptoms related to not having enough normal blood cells, such as:

  • Weakness, shortness of breath, and pale skin due to a lack of red blood cells (anemia)
  • Bleeding and bruising due to a lack of platelets (thrombocytopenia)
  • Fever and infections due to a lack of normal infection-fighting white blood cells (leukopenia)

Other signs and symptoms may include:

  • Bone and joint pain
  • Enlarged lymph nodes, spleen, liver, kidneys, and/or testicles
  • Headaches
  • Vomiting
  • Confusion and seizures (when excess cells collect in the brain or central nervous system)
  • Unexplained weight loss
  • Night sweats

Chronic leukemias often progress slowly, may have no early symptoms, or may cause milder forms of the same symptoms noticed with acute leukemia. Chronic leukemia may be found by chance during a routine check-up before any symptoms are noticed. Some cases may be monitored for years before treatment is required, while others may be more aggressive. If leukemia cells begin dividing more quickly, they may cause a blast crisis (progression to acute leukemia), leading to the production of only immature cells and a rapidly worsening condition. Chronic leukemia symptoms include:

  • Feeling tired or rundown
  • Unexplained weight loss, loss of appetite
  • Shortness of breath during normal physical activity
  • Pale skin
  • Pain or discomfort on the upper left side of the stomach (caused by an enlarged spleen)
  • Night sweats
  • Bruising and bleeding easily
  • Fever


Laboratory Tests
A number of laboratory tests may be used to help diagnose leukemia, determine the type, and monitor the effectiveness of treatment. After successful treatment (remission), testing may be used to check whether leukemia has returned.

General blood tests may include:

  • Complete blood count (CBC) and WBC differential. These are groups of routine tests that evaluate the cells that circulate in blood. They count the number of cells and determine the maturity and proportion of different types of cells. These tests may provide the first evidence of leukemia. Abnormal results, such as elevated white blood cell counts or low red blood cell counts, can be due to leukemia but are also see in a variety of temporary or chronic conditions. However, blasts (immature blood cell precursors) are not normally seen in the blood, so if they are present, some kind of leukemia is likely and follow-up testing will be ordered. The CBC and differential are also important tools to monitor the effectiveness of treatment and to detect disease recurrence.
  • Blood smear. A blood smear, or peripheral blood smear, is often used to follow up a CBC with abnormal white blood cells, red blood cells or platelets, or with unclear results. A drop of blood is smeared on a microscope slide and examined for immature cells or cells with abnormal sizes, shapes or appearance compared to normal cells.
  • Bone marrow aspiration/biopsy. If a healthcare practitioner suspects leukemia, a bone marrow aspiration and/or biopsy procedure will be done to look at the tissue in the marrow. A pathologist or other specialist examines the marrow sample (bone marrow tissue biopsy and/or liquid marrow smear) using a microscope, evaluating the number, size, and appearance of each of the cell types as well as the proportions of mature and immature cells. If leukemia is present, the type and severity of the disease can be determined. This test will also help establish a baseline for bone marrow cells, to see how they respond to treatment.

Select tests may include:

  • Spinal tap (lumbar puncture) and cerebrospinal fluid analysis. If leukemia is found in the bone marrow, a lumbar puncture (spinal tap) may also be done to help determine whether the cancer has spread to the central nervous system and cerebrospinal fluid (CSF). If leukemic cells are seen in the CSF, additional treatment (for example, direct injection of drug into the CSF space) may be necessary.
  • Immunophenotyping or phenotyping by flow cytometry and/or immunohistochemistry. This test can be used to help diagnose leukemia and to determine the type. (Read the article on Immunophenotyping for additional details.)
  • Cytogenetic tests (FISH and karyotyping). These tests look at chromosome structure and number.
    • Chromosome analysis (karyotyping) is a cytogenetic test that maps the 46 chromosomes in cells to look for changes in arrangement, size, or number (including deletions or translocations) that are associated with leukemia.
    • Fluorescent in situ hybridization (FISH) is a cytogenetic test that looks for changes in chromosomes that come from genetic variations. It is generally more sensitive than karyotyping. In FISH, an abnormal gene segment in a chromosome is made to “light up” or fluoresce when it is bound by a special probe. FISH helps diagnose different leukemias that may look similar but have different genetic abnormalities and therefore may require different treatment. For more on this, see the article The Universe of Genetic Testing: Genetic Testing Techniques.
  • Molecular testing. One factor that contributes to the uncontrolled growth of cancer cells is malfunctioning proteins that control cell growth and development. Those malfunctions can result from abnormalities in DNA from mutations (disease-causing genetic variants). Lab tests detect those abnormalities associated with certain types of leukemia. They can help guide treatment and/or determine prognosis for a certain leukemia and sometimes monitor effectiveness of treatment. Some common tests and their associated leukemia types include:
    • Acute promyelocytic leukemia [PML-RARA ]
    • Acute myeloid leukemia [AML1-ETO, CBFB-MYH11, NPM1 mutation, CEBPA mutation, FLT3 mutation]
    • Acute lymphoblastic leukemia [TEL-AML1, IL3-IGH, BCR-ABL]
    • Myeloid or lymphoid neoplasm with eosinophilia [FlP1L1-PDGFRA]
    • Chronic myelogenous leukemia [BCR-ABL]
  • Minimum residual disease (MRD) tests. These are relatively new, more sensitive flow cytometry or PCR-based tests to detect very small amounts of leukemic cells post-treatment, known as minimum residual disease (MRD). This can help guide treatment and prevent relapses after the leukemia has gone into remission.
  • DNA sequencing may be used to detect many potential gene mutations simultaneously and to help guide patient management, including treatment and outcome prediction.

Non-Laboratory Tests
Computerized tomography (CT), magnetic resonance imaging (MRI), chest x-rays, or positron emission tomography (PET) scans are sometimes used to look for signs of the disease (tumors and masses of cells) in areas such as the chest. Other imaging scans, like ultrasound, may also be used to evaluate the health of body organs such as the spleen, liver, and kidney. For more on these, see RadiologyInfo.org.


In general, cure and remission rates of leukemia continue to improve for both children and adults.

Specific treatment depends on the type of leukemia, severity, and symptoms. For example, people with CLL may not need treatment until they show signs and symptoms while people with ALL often need aggressive treatment.

The goals of treatment are to address the cell shortages that are causing symptoms, induce remission, and, if possible, kill all of the abnormal leukemia cells, allowing normal cells to develop and restore normal bone marrow function. Since treatment options continually evolve, it is important to make individual decisions with a healthcare provider, typically a cancer specialist (oncologist) familiar with the most recent research.

Leukemia treatment may include a combination of the following:

  • Chemotherapy—drugs that stop the growth of cancer cells by killing them or stopping them from dividing
  • Radiation—high-energy x-rays that kill cancer cells or stops their growth
  • Hematopoietic stem cell transplant—stem cells are given after all the cancer cells have been destroyed by chemotherapy and radiation therapy. The stem cells replace the healthy blood cells that were killed along with the leukemia cells.
  • Targeted therapy—cancer drugs that inhibit or target very specific proteins associated with certain cancers have been developed. Two examples are tyrosine kinase inhibitors and anti-leukemia antibodies. Genetic tests detect the presence of mutations in cancer tissue that tell a healthcare practitioner whether the person being tested is likely to benefit from this specific therapy.

In addition to these treatments, researchers are continuing to investigate new types of therapies to achieve remission and prolong the lives of people with leukemia. For example, immunotherapy (e.g., chimeric antigen receptor T cells or CAR-T cells) is being researched as a treatment for certain leukemia. Immunotherapy is designed to boost the body’s natural immune system to fight the cancer.

Some people with leukemia may want to consider enrollment in clinical trials of new treatments. There are promising areas of research that may offer them additional options. For more on this, see Clinicaltrials.gov. For additional details on treatment, see the links under Related Content.

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