Yes, leukemia is cancer, but it starts in blood-forming cells rather than in a solid tumor
Leukemia is a type of cancer that begins in the bone marrow—the soft tissue inside bones where blood cells are made. Instead of producing healthy blood cells in the right amounts, the bone marrow starts making abnormal white blood cells that multiply out of control. These leukemia cells crowd out normal blood cells, which is why leukemia behaves differently from cancers that form lumps in organs like the lungs or breast.
The key difference is location and form. Most cancers grow as solid tumors you could potentially see on an X-ray or feel as a lump. Leukemia spreads through the bloodstream and bone marrow as individual cells rather than as a mass. This is why leukemia is sometimes called a "liquid cancer"—it circulates through your body in your blood rather than staying in one place.
Key Takeaways
- Leukemia is cancer that starts in bone marrow cells that produce blood, not in a solid organ or tissue.
- The four main types are acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML)—divided by how fast they grow and which blood cells are affected.
- Leukemia cells multiply uncontrollably and crowd out normal white blood cells, red blood cells, and platelets, which causes the symptoms people experience.
- Treatment depends on the type, how fast it is growing, and the person's age and overall health, and may include chemotherapy, targeted drugs, or stem cell transplant.
How leukemia develops in bone marrow
Your bone marrow constantly produces three types of blood cells: white blood cells (which fight infection), red blood cells (which carry oxygen), and platelets (which help blood clot). In leukemia, a mutation occurs in a single blood-forming cell, and that cell begins to divide repeatedly without the normal stop signals. Over time, these abnormal cells outnumber the healthy ones.
As leukemia cells take over the bone marrow, there is less room for normal blood cells to develop. This causes a cascade of problems: too few red blood cells leads to anemia and fatigue, too few platelets causes easy bruising and bleeding, and too many abnormal white blood cells means the immune system cannot work properly. The leukemia cells can also spill into the bloodstream and travel to other organs like the liver, spleen, and brain.
The four main types of leukemia
Leukemia is classified two ways: by how fast it grows (acute or chronic) and by which type of white blood cell is affected (lymphoid or myeloid). This creates four main categories.
Acute lymphoblastic leukemia (ALL) grows very quickly and affects lymphoid cells. It is the most common leukemia in children but also occurs in adults. Acute myeloid leukemia (AML) grows quickly and affects myeloid cells; it is more common in adults. Both acute forms require urgent treatment because the cancer progresses rapidly.
Chronic lymphocytic leukemia (CLL) grows slowly and affects lymphoid cells; it is most common in people over 70. Chronic myeloid leukemia (CML) grows slowly and affects myeloid cells. Chronic forms may not cause symptoms for years, and some people are diagnosed by chance during a routine blood test.
Symptoms that may appear
Acute leukemia often causes symptoms that develop over days or weeks: extreme fatigue, frequent infections, unexplained bruising or bleeding (including nosebleeds or bleeding gums), bone or joint pain, and swollen lymph nodes, liver, or spleen. Some people have a fever or notice tiny red or purple spots on the skin (petechiae) from bleeding under the skin.
Chronic leukemia may cause no symptoms at all in early stages. When symptoms do appear, they are often mild and nonspecific: tiredness, loss of appetite, or a feeling of fullness in the upper left abdomen (from an enlarged spleen). Because these symptoms are vague, chronic leukemia is sometimes found by chance when a blood test is done for another reason.
How leukemia is diagnosed
Diagnosis begins with a complete blood count (CBC), a standard blood test that measures the number and types of cells in your blood. If the CBC shows abnormal results—too many white blood cells, too few red blood cells or platelets, or the presence of immature cells—the next step is a bone marrow biopsy.
During a bone marrow biopsy, a doctor uses a needle to remove a small sample of bone marrow, usually from the hip bone. A pathologist examines the sample under a microscope to identify the type of leukemia cells present. Additional tests may include flow cytometry (which identifies cell types using fluorescent markers) and cytogenetics (which looks for specific genetic changes in the cancer cells). These tests help determine which type of leukemia it is and guide treatment decisions.
Treatment approaches vary by type and stage
Treatment for leukemia depends on the type, how fast it is growing, whether it has spread, the person's age, and their overall health. Acute leukemias are treated aggressively because they progress quickly; the goal is to achieve remission (when leukemia cells are no longer detectable in the bone marrow).
Chemotherapy is the primary treatment for most leukemias. It uses drugs to kill rapidly dividing cells, including leukemia cells. Targeted therapy drugs work differently—they target specific genetic mutations found in leukemia cells, which can be more effective and have fewer side effects than traditional chemotherapy. Stem cell transplantation (also called bone marrow transplant) may be used for certain types or in cases where chemotherapy alone is not sufficient; it involves replacing the diseased bone marrow with healthy cells from a donor or from the patient's own cells collected before treatment.
Chronic leukemias, especially CML, may be managed with targeted drugs that can keep the disease under control for years without chemotherapy. Some people with early-stage chronic leukemia may not need immediate treatment but are monitored closely with regular blood tests.
Survival and long-term outlook
Survival rates for leukemia vary widely depending on the type, age at diagnosis, and how well the leukemia responds to treatment. Acute lymphoblastic leukemia in children has improved dramatically over the past few decades, with five-year survival rates now above 90 percent in many developed countries. Acute myeloid leukemia in adults has lower survival rates but has also improved with newer treatments.
Chronic leukemias generally have better long-term survival than acute forms because they grow more slowly. Many people with CML now have near-normal life expectancy with targeted drug therapy. Chronic lymphocytic leukemia progresses slowly, and some people live for many years with minimal symptoms or treatment.
Remission does not always mean cure. Some people remain in remission for years or decades; others experience relapse, where leukemia cells return. Ongoing monitoring with blood tests is standard after treatment ends, and the frequency depends on the type of leukemia and the individual's response to therapy.
Frequently Asked Questions
Is leukemia always fatal?
No. Many people with leukemia go into remission and live for years or decades. Survival depends on the type, how early it is caught, age at diagnosis, and how well the person responds to treatment. Children with ALL and people with CML on targeted therapy often have very good long-term outcomes.
Can you catch leukemia from someone else?
No, leukemia is not contagious. It develops when a mutation occurs in a person's own bone marrow cells. You cannot catch it from another person through contact, blood, or any other means.
What causes leukemia?
The exact cause is usually unknown. Risk factors include exposure to high-dose radiation, certain chemicals (like benzene), smoking, some genetic conditions, and a family history of leukemia. However, most people with leukemia have no known risk factors, and most people exposed to these risk factors never develop leukemia.
Is leukemia the same as lymphoma?
No. Both are blood cancers, but they start in different cells. Leukemia starts in bone marrow and circulates in the blood. Lymphoma starts in lymph nodes and other lymphoid tissues. They are diagnosed and treated differently.
Can children get leukemia?
Yes. Leukemia is the most common cancer in children, though it is still rare overall. Acute lymphoblastic leukemia is the most common type in children. Treatment has improved significantly, and most children with ALL now survive into adulthood.