Leukemia is cancer that starts in blood-forming cells in your bone marrow

Leukemia begins when cells in your bone marrow—the soft tissue inside your bones where blood cells are made—start to grow abnormally. Instead of maturing into healthy red blood cells, white blood cells, or platelets, these cells multiply rapidly and crowd out the normal ones. The result is too many immature or abnormal white blood cells in your bloodstream, which weakens your immune system, causes anemia, and makes you bleed or bruise easily.

Unlike solid tumors, leukemia does not form a lump. It spreads through the blood and can reach your organs, lymph nodes, and central nervous system. The disease develops over weeks to months in acute forms, or over years in chronic forms.

Key Takeaways

  • Leukemia starts in bone marrow when blood-forming cells begin to multiply abnormally instead of maturing into healthy blood cells.
  • The four main types are acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML), each with different progression rates and treatment approaches.
  • Common symptoms include fatigue, frequent infections, unusual bruising or bleeding, and swollen lymph nodes, though some people have no symptoms early on.
  • Diagnosis requires blood tests and bone marrow biopsy; treatment depends on the type, stage, and your age and overall health.

The four main types of leukemia and how they differ

Acute lymphoblastic leukemia (ALL) develops quickly and affects lymphoid cells, which normally become B and T cells that fight infection. It is most common in children but also occurs in adults. Without treatment, it worsens within weeks.

Acute myeloid leukemia (AML) develops quickly and affects myeloid cells, which normally become red blood cells, platelets, and certain white blood cells. It is the most common acute leukemia in adults. It also progresses rapidly without treatment.

Chronic lymphocytic leukemia (CLL) develops slowly and affects lymphoid cells. Many people have no symptoms for years and discover it by chance during routine blood work. It is most common in adults over 70.

Chronic myeloid leukemia (CML) develops slowly and affects myeloid cells. It is often found in the chronic phase, when symptoms are mild or absent. Without treatment it eventually speeds up into a blast phase, which behaves like acute leukemia.

Symptoms that may signal leukemia

Early symptoms are often vague and easy to mistake for other illnesses. Fatigue and weakness happen because abnormal cells crowd out red blood cells, leaving you anemic. Frequent infections occur because the abnormal white cells do not fight germs effectively. Unusual bruising, nosebleeds, or bleeding gums happen because leukemia cells reduce platelet production.

Other symptoms include swollen lymph nodes (felt as lumps in your neck, armpits, or groin), an enlarged spleen or liver, bone or joint pain, and night sweats. Some people have no symptoms at all, especially in chronic forms, and learn they have leukemia only when a blood test is done for another reason.

Symptoms vary widely depending on the type and how fast the disease is progressing. If you have persistent fatigue, repeated infections, or unexplained bruising, your doctor can order blood tests to investigate.

How leukemia is diagnosed

Diagnosis starts with a complete blood count (CBC), a blood test that measures the number and types of cells in your blood. If the CBC shows abnormal results, your doctor will order additional tests.

A bone marrow biopsy is usually the next step. A needle is inserted into the hip bone to remove a small sample of marrow, which is then examined under a microscope to identify the type of leukemia and check for genetic mutations. This test confirms the diagnosis and helps determine which treatments will work best.

Other tests may include flow cytometry (which identifies the exact type of leukemia cell), cytogenetics (which looks for chromosome changes), and imaging scans to check whether leukemia has spread to organs or the central nervous system. These results together determine your prognosis and guide treatment decisions.

Risk factors and causes

Most people who develop leukemia have no known risk factor. However, certain things increase the odds: exposure to high levels of radiation, long-term exposure to benzene (a chemical in gasoline and some industrial products), smoking, and previous chemotherapy or radiation for another cancer.

Some genetic conditions raise risk, including Down syndrome and neurofibromatosis. A family history of leukemia increases risk slightly, though most leukemias are not inherited. Age matters too—acute leukemias can occur at any age but are most common in children and older adults, while chronic leukemias are more common in people over 55.

Having a risk factor does not mean you will develop leukemia. Many people with risk factors never get the disease, and many people without any known risk factors do.

How treatment is chosen

Treatment depends on the type of leukemia, whether it is acute or chronic, your age, overall health, and genetic features of the cancer cells. Acute leukemias require immediate treatment, usually chemotherapy, sometimes combined with targeted drugs or stem cell transplant. Chronic leukemias may be monitored without treatment if they are progressing slowly, or treated with oral medications if they are active.

Chemotherapy uses drugs to kill leukemia cells but also affects healthy cells, causing side effects like nausea, hair loss, and increased infection risk. Targeted therapies attack specific mutations in leukemia cells and often have fewer side effects. Stem cell transplant (also called bone marrow transplant) replaces diseased marrow with healthy cells from a donor or from your own cells collected and treated beforehand.

Newer immunotherapies train your immune system to recognize and destroy leukemia cells. Your oncology team will discuss which approach or combination makes sense for your situation, the expected timeline, and what to expect during and after treatment.

Survival rates and long-term outlook

Survival varies widely by type, age, and genetic factors. Five-year survival rates—the percentage of people alive five years after diagnosis—range from under 10 percent for some forms of AML in older adults to over 90 percent for ALL in children. CLL and CML often have longer survival because they progress slowly, and many people live for years or decades with the disease managed by medication.

Advances in treatment over the past decade have improved outcomes, especially for younger patients and those with certain genetic mutations. Remission (when leukemia cells are no longer detectable) is possible with most types, though some people relapse and need additional treatment.

Your doctor can discuss your specific prognosis based on your type, stage, age, and test results. Prognosis is not a prediction of what will happen to you individually—it is a statistical average based on many people with similar disease.

Frequently Asked Questions

Is leukemia the same as lymphoma?

No. Leukemia starts in bone marrow and spreads through the blood. Lymphoma starts in lymph nodes or other lymphoid tissue. Both are blood cancers, but they develop differently and are treated differently. A blood test can distinguish between them.

Can leukemia run in families?

Most leukemias are not inherited. However, having a close relative with leukemia raises your risk slightly. Some genetic syndromes (like Down syndrome) increase leukemia risk and do run in families. Talk to your doctor or a genetic counselor if multiple family members have had leukemia.

What happens during a bone marrow biopsy?

A needle is inserted into the back of your hip bone to remove a small sample of marrow. The area is numbed first, so you feel pressure but not sharp pain. The procedure takes 10 to 15 minutes. Some soreness at the site is normal for a few days afterward.

Can children survive leukemia?

Yes. Childhood leukemia, especially ALL, has high survival rates—over 85 percent five-year survival for ALL and around 70 percent for AML. Treatment is intensive but many children go on to live normal lives. Long-term side effects from treatment are possible and monitored over time.

What is the difference between remission and cure?

Remission means leukemia cells are no longer detectable in blood or bone marrow tests. Cure means the disease will never return. Doctors use remission because some leukemias can recur years later. Long-term remission, especially in chronic leukemias, can last decades.