Acute myeloid leukemia (AML) is one type of cancer of the bone marrow and blood. It is also called acute myelogenous leukemia or acute myelocytic leukemia.
What is acute myeloid leukemia?
In people with AML, some blood stem cells begin to function abnormally, producing immature myeloid cells, also called blasts, that transform into cancer.
- Unlike normal blasts, the leukemic blasts don’t mature into red blood cells, white blood cells or platelets.
- The leukemic blasts interfere with the ability of normal blasts to mature.
- This increases the number of blasts in your body and reduces the number of normal mature blood cells.
- Leukemic blasts can travel around your body through your bloodstream and interfere with the function of your organs.
AML gets worse quickly and may lead to serious infections and organ failure if it is not treated, so it is important to start treatment fairly soon after diagnosis. But to optimize your treatment, your doctors may recommend waiting for test results that provide details about your specific AML.
Understanding your bone marrow and blood
To understand leukemia, it helps to know the basics about your bone marrow and blood cells.
What are stem cells?
Stem cells are cells in your body that have the potential to turn into any kind of cell, such as a skin cell, liver cell, brain cell or blood cell. Stem cells that turn into blood cells are called hematopoietic stem cells, or blood stem cells.
Why are blood stem cells important?
When blood cells become old or damaged, they die, and blood stem cells produce new blood cells to replace them. Blood stem cells are mainly found in bone marrow (the soft, spongy tissue inside your bones), but some are also found in circulating blood.
Blood stem cells produce myeloid stem cells and lymphoid stem cells.
- Myeloid stem cells produce myeloblasts, which in turn produce white blood cells, known as granulocytes, as well as red blood cells and platelets.
- Lymphoid stem cells produce lymphoblasts, which in turn produce several types of white blood cells.
What do healthy blood cells do?
Healthy white blood cells, red blood cells and platelets are essential.
- White blood cells fight infection.
- Red blood cells carry oxygen from your lungs to other parts of your body and take carbon dioxide back to your lungs to be removed.
- Platelets make your blood clot and slow or stop bleeding.
Symptoms of AML
Many of the signs and symptoms of AML are similar to the flu or other common, less serious diseases. Check with your doctor if you have any of these.
Symptoms from low white blood cells:
- Flu-like symptoms, such as fever, sweats and body aches
- Mouth inflammation, pain or sores
Symptoms from low red blood cells:
- Shortness of breath
- Pale skin
- Fatigue, weakness, lack of energy or sleepiness
Symptoms from low platelets:
- Bleeding from your gums
- Red spots on your palate or ankles
- Easy bruising or prolonged bleeding from cuts
- Frequent or severe nosebleeds
Other general symptoms:
- Loss of appetite
- Unexplained weight loss
- Pain or aches in your bones or joints
- Swollen abdomen
- Swollen lymph nodes in your neck, underarm, groin or stomach
- Headaches, dizziness
If your doctor suspects you may have leukemia, they will want to perform a thorough physical examination and talk with you about your medical history.
An accurate diagnosis of AML requires several tests. You might have any or all of these.
- Blood tests — to check the types and numbers of blood cells, check the amount of hemoglobin (protein that carries oxygen), look for blasts and examine the shape of your blood cells (complete blood count and peripheral blood smear) and to see if leukemic cells are present and which type they are (immunophenotyping, or flow cytometry).
- Bone marrow tests — taking samples of bone marrow and a small piece of bone from your pelvis using a needle (bone marrow aspiration and biopsy) and checking them for leukemic cells.
- Chromosome tests — checking your blood or bone marrow cells for changes in chromosomes, such as missing parts of chromosomes or two chromosomes that have exchanged some DNA. These tests include cytogenetic analysis, fluorescent in situ hybridization and polymerase chain reaction.
- Lumbar puncture — taking a sample of cerebrospinal fluid from your spine with a needle to check whether leukemia has spread to your spinal cord and brain.
- Imaging tests — such as chest X-ray, computed tomography (CT) scan, magnetic resonance imaging (MRI) scan or ultrasound to check whether leukemia is impacting other parts of your body.
Subtypes of AML
To help plan your treatment, your team will use your test results to tell which subtype of AML you have. AML is divided into subtypes based on:
- How mature the leukemic cells are
- How different the leukemic cells are from normal cells
- The chromosome abnormalities in the cells
AML is grouped into the following subtypes, and each of these may be further split into groups.
- AML with characteristic cytogenetic abnormalities
- AML with mutations of the FLT3, NPM1 or CEBPA gene
- AML with myelodysplasia-related changes
- Therapy-related AML (applies to people who received chemotherapy or radiation therapy for another type of cancer — up to 20 percent of people with AML)
- AML not otherwise categorized
- Acute leukemias of ambiguous lineage
- Myeloid sarcoma
- Myeloid proliferation related to Down syndrome
Acute promyelocytic leukemia
Acute promyelocytic leukemia (APL) is an aggressive subtype of AML. It is characterized by an exchange of the PML gene on chromosome 15 and the RARα gene on chromosome 17 — written as t(15;17). Treatment for APL is unique. It requires different medications than doctors typically give for other types of AML.
Most cancers are assigned a numbered stage based on the size of the tumor and how far the disease has spread. Typically, leukemia doesn’t form a solid tumor and it is found throughout the body, so there is no formal staging system for AML.
Instead, AML is classified as:
- Newly diagnosed AML, or untreated AML. Treatment may have begun for relief of symptoms, such as fever and bleeding, but treatment has not begun for the leukemia.
- AML in remission. After treatment, you may be considered in remission if your complete blood count is normal, your bone marrow has no more than 5 percent leukemia cells and you have no signs or symptoms of leukemia.
- Relapsed AML, or recurrent AML. This means your leukemia returned after going into remission.
- Refractory AML. This means the leukemia has not entered remission, despite treatment with a least two courses of chemotherapy.
Risk stratification in AML
Doctors use a method called risk stratification to help predict how likely your disease is to respond to treatment and what the outlook is.
- If you’re newly diagnosed and you haven’t had any AML treatment yet, your risk level is based in large part on whether your AML has genetic abnormalities and, if it does, which type.
- Once you’ve had treatment, other factors come into play, such as whether there’s any sign of AML in your body or, if your AML came back, how long it was in remission.
Your doctor can explain your risk level and how it affects your treatment plan.
How common is AML?
About 21,000 people are diagnosed with AML each year in the U.S. AML is the most common type of acute leukemia in adults.
What causes AML?
Doctors do not know what causes AML. The disease typically affects older people — the average age is 66. It is also slightly more common in males than females.
The few known risk factors include:
- Being exposed to certain chemicals, such as chemotherapy or benzene
- Being exposed to high levels of radiation
- Having certain blood disorders, such as myeloproliferative neoplasms or myelodysplastic syndromes
- Having certain genetic conditions, such as Down syndrome
- Having a family history of AML, such as having a parent or sibling with AML, especially an identical twin who had AML as an infant or young child
Keep in mind that most people who develop AML have none of these risk factors, and most people with these risk factors do not develop the disease.