Quick Links
Resources
About MyLeukemiaTeam
Powered By
Leukemia is a type of blood cancer that affects leukocytes — white blood cells (WBCs) — that are part of the immune system. Leukemia begins when blood stem cells in the bone marrow develop genetic mutations (changes) in the genes. These changes affect how quickly WBCs grow and allow them to survive longer than they should. This buildup of abnormal cells crowds out healthy cells. Types of leukemia differ based on which WBCs develop mutations and how fast they grow.
Covering every type of leukemia is beyond the scope of this article. Instead, we’ll discuss the four main types of leukemia and some common subtypes.
There are four main types and many subtypes of leukemia. Each type of leukemia may need a different treatment, and the prognosis (outlook) can vary based on many factors. Your cancer care team will diagnose the specific type of leukemia you have, which helps them decide which treatment options are most likely to work well for you.
Read on to learn more about how leukemia is categorized, or go straight to one of the four main types of leukemia:
Leukemia can be classified as acute or chronic, depending on how quickly it develops and the type of white blood cells involved. Acute leukemia happens when immature WBCs — cells that haven’t fully developed yet — start growing uncontrollably. This means the disease progresses quickly and needs prompt treatment. Chronic leukemia, on the other hand, involves mature WBCs. These cells are more developed but still abnormal, and the disease usually progresses more slowly over time.
In the bone marrow, all blood cells start as blood-forming stem cells. These cells can develop into any type of blood cell. Stem cells then divide into one of two parent cells — myeloid or lymphoid. These parent cells form the two main branches of the blood cell family.
Myeloid parent cells develop further into:
Lymphoid parent cells form all of the lymphoid cells (or lymphocytes). Lymphocytes include:
Each type of blood cell undergoes several stages of development before becoming a mature, functional cell. After establishing the stage of development of the abnormal cells, oncologists will often order genetic testing to find out which mutations are responsible.
Cytogenetic testing examines the chromosomes of cancer cells for specific mutations. This is used as part of the process of diagnosing leukemia. Some genetic mutations can confirm a leukemia diagnosis. Other mutations can help predict which leukemia treatments will work or tell how fast the cancer will progress.
Different genetic changes are linked to various types of leukemia. For example, during cell division, chromosomes 9 and 22 sometimes swap sections, creating a changed version of chromosome 22 called the Philadelphia chromosome. Named after the city where it was first found, this changed chromosome leads to the BCR-ABL gene fusion, which causes cells to grow too much and live longer than normal. The BCR-ABL gene fusion occurs in many types of leukemia, including CML and ALL. CML and ALL subtypes are Philadelphia-positive or Philadelphia-negative. Health care teams may recommend different treatments based on this classification.
Similar situations apply to many other genetic mutations in other types of leukemia.
Most cases of leukemia fall under four main categories. Many of these categories also have several subtypes. Some types of leukemia are further classified by stage or phase.
ALL is an acute form of leukemia that involves lymphoid cells in earlier stages of development. ALL is the most common type of leukemia in children and young adults under 25. The risk of developing ALL is highest in children under the age of 5 years. The risk for ALL decreases through the 20s, then rises again after age 50. However, it’s rare for adults to develop ALL. Other names used for ALL are acute lymphocytic leukemia and acute lymphoid leukemia.
In the past, the French-American-British (FAB) classification for ALL was used. The FAB system describes leukemia based on how cancer cells look under the microscope from biopsy samples. Today, most health care teams use the World Health Organization (WHO) system. The WHO system classifies types of ALL based on genetic changes. The WHO system defines the two main subtypes of ALL based on whether B cells or T cells become cancerous.
The most common subtype of ALL is B-ALL. It involves immature cells that would become B cells. B-ALL accounts for 88 percent of ALL cases in children and 75 percent of adult ALL cases. B-ALL may be further subdivided by the specific genetic abnormalities of the cancer cells. There are many subtypes of B-ALL based on genetic mutations. Some examples include:
T-ALL develops from immature cells that become T cells. T-ALL occurs more often in adults, making up 25 percent of ALL cases in adults and 12 percent of cases in children. Cancer Research UK reports that T-ALL is more likely to develop in males than females.
The prognosis for ALL depends on many factors, including:
Younger people tend to have a better prognosis with ALL, but prognosis decreases with age. ALL can spread from the bone marrow to the liver, lymph nodes, brain, and testes. After treating ALL, it’ll either be in remission — no signs of disease after treatment — or it will be an active disease. People who achieve complete remission have better outcomes than those whose ALL doesn’t respond to treatment.
AML is an acute form of leukemia involving myeloid cells in earlier stages of development. AML is the most common type of acute leukemia in people aged 25 to 49 years and in those aged 50 to 64. AML can also develop in children. It’s also referred to as:
AML has two different classification systems. The FAB classification of AML was developed in the 1970s. The type of WBCs involved and the stage of maturity of the cells determine the subtypes named M0 through M7. The WHO updated its classification system for AML in 2022. These updates focus on specific genetic/underlying causes and factors that affect prognosis.
AML progresses rapidly without treatment. AML is a fast-moving type of leukemia that can spread to other sites of the body, including:
The prognosis for AML depends on many factors, including a person’s age and medical history, the subtype of AML, and whether cancer has spread to the CNS.
AML isn’t classified in stages like some types of cancer. AML classifications are either untreated/in remission or recurrent. Recurrent disease is when the cancer progresses again after a period of remission. Treatment options for AML depend on many factors.
Like ALL, CLL usually involves B cells but sometimes affects T cells. CLL mirrors small lymphocytic lymphoma (SLL), a form of non-Hodgkin lymphoma. CLL and SLL are so similar that they’re considered different expressions of the same disease. In CLL, cancer cells are mostly found in the bone marrow and blood. In SLL, cancer cells are found in the lymph nodes and other lymphoid tissues.
Although CLL is considered a chronic form of blood cancer, in some cases, it can progress rapidly. CLL is common in older adults and is the most common type of leukemia in people aged 65 and over. The risk of developing CLL increases with age. Lymphoma Action, a UK charity dedicated to supporting people affected by lymphoma, notes that CLL is more than twice as common in men as in women.
Monoclonal B-lymphocytosis (MBL) is a condition in which someone has CLL-like cells that may or may not develop into CLL. Between 1 percent and 2 percent of those with MBL develop CLL each year.
CLL can be categorized based on how fast it’s growing, which type of lymphocyte is involved (B or T), which organs are involved, and the stage of the cancer.
CLL can be described as indolent (slow-growing) or aggressive (fast-growing). Indolent CLL may not need immediate treatment in some cases. However, indolent cases of CLL can transform into a more aggressive form. It’s important to treat aggressive CLL early.
CLL is classified by which type of WBCs become cancerous. B-cell CLL accounts for more than 95 percent of cases of CLL. T-cell prolymphocytic leukemia is found in 1 percent of people with CLL.
Unlike most other forms of leukemia, CLL stages reflect the spread of the disease in the body. The two classification systems for CLL stages are the Rai Staging System and the Binet Classification System.
The prognosis for CLL varies based on many factors, including:
Some genetic mutations have a better prognosis than others.
CML develops in myeloid cells. CML is also referred to as:
CML is also considered to be a type of myeloproliferative neoplasm, a rare category of blood cancer closely related to leukemia. CML is slow-growing but can transform into a more aggressive form that’s harder to treat.
CML accounts for about 15 percent of leukemia cases in adults. Nearly half of CML cases are diagnosed in people aged 65 or older. CML is rare in children and is slightly more common in men than in women, according to the Leukemia & Lymphoma Society.
The two phases of CML are chronic and blastic. Symptoms and treatment options vary, depending on the phase. Phases are distinguished by the ratio of cancer cells to healthy cells in the bone marrow and blood.
Without treatment, CML will progress to the blastic phase within three to four years after diagnosis. CML that relapses or fails to respond to treatment is called resistant CML.
The prognosis for those with CML varies based on many risk factors, including:
Some types of leukemia are more difficult to classify. Undifferentiated acute leukemia involves cancerous cells, which can resemble more than one type of leukemia, making it hard to categorize. Biphenotypic acute leukemia includes cancerous cells that show features of two different types of leukemia at the same time. These are grouped together under the classification of acute leukemia of ambiguous lineage (ALAL). Others may share traits with blood cancers, such as lymphoma or myelodysplastic syndromes. These subtypes tend to be harder to treat and have worse outcomes than other types of leukemia.
Several rarer forms of leukemia relate to CLL but with some differences. These include:
Leukemia comes in many forms, each with unique challenges and treatment approaches. Understanding the type and how it develops helps doctors tailor the most effective treatment plan. Some types require immediate treatment, while others may only need regular monitoring. If you or someone you care about is facing leukemia, there are plenty of resources and support to help you navigate every step of the journey.
On MyLeukemiaTeam, the social network for those with leukemia and their loved ones, more than 20,000 members gather to ask questions, give advice, and share their stories with others who understand life with leukemia.
Have you or someone you know recently been diagnosed with a type of leukemia? Have you talked to your health care team to understand how cancer care can vary depending on the type of leukemia? Share your comments below, or start a conversation by posting on your Activities page.
Todd Gersten, M.D.
is a hematologist-oncologist at the Florida Cancer Specialists & Research Institute in Wellington, Florida. Review provided by VeriMed Healthcare Network.
Learn more about him here.
Kelly Crumrin
is a senior editor at MyHealthTeam and leads the creation of content that educates and empowers people with chronic illnesses.
Learn more about her here.
Get updates directly to your inbox.
Can You Provide Information About Chronic Eosinophilia Lukia.
I Know It Says Age 65 And Up My Husband Was Diagnosed At Age 57 Is That Good Are Bad ?
]=any Info About Cmml?
Can I Get Information On CMML?
What Is MDS Leukemia
Become a member to get even more:
Your Privacy Choices
A MyLeukemiaTeam Member
Anyone have a low INR thin blood before there diagnosis I went to the low blood platelet level and free bleeding just from a little bump on my arm
We'd love to hear from you! Please share your name and email to post and read comments.
You'll also get the latest articles directly to your inbox.