Leukemia does not usually begin in a specific solid organ such as the liver, spleen, or kidneys. It is a cancer of the blood-forming tissues, and many types of leukemia begin in the bone marrow, where blood cells are produced.
As abnormal leukemia cells multiply, they can enter the bloodstream and may accumulate in other parts of the body. Depending on the type of leukemia, the lymph nodes, spleen, liver, brain and spinal cord, skin, or other organs may become involved.
Understanding where leukemia begins and how it can affect other parts of the body is important when learning about the disease and its blood cancer treatment.
Where Does Leukemia Begin?
For most leukemias, the starting point is the bone marrow. Bone marrow is the soft tissue inside certain bones where blood-forming stem cells develop into red blood cells, white blood cells, and platelets. In leukemia, abnormal blood-forming cells multiply and interfere with the normal production of healthy blood cells.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
As the abnormal cells increase, they can crowd the bone marrow and reduce the production of normal:
- Red blood cells, potentially causing anemia and fatigue
- White blood cells, affecting the body's ability to fight infections
- Platelets, increasing the tendency to bruise or bleed
For this reason, the effects of leukemia can become noticeable throughout the body even though the disease begins in blood-forming tissue.
Does Leukemia Start in the Blood?
Leukemia is commonly described as a cancer of the blood and bone marrow, but the abnormal cells generally originate from blood-forming cells in the bone marrow.
As leukemia cells are produced in large numbers, they can enter the bloodstream. A blood test may therefore reveal abnormal blood-cell counts or abnormal cells even though the underlying disease originated in the blood-forming system. This is different from many solid cancers, which begin as a tumor in a particular organ or tissue.
Which Parts of the Body Can Leukemia Affect?
Once leukemia cells are present in the blood and bone marrow, they can accumulate in other tissues. The organs and tissues affected can vary according to the type of leukemia.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Bone marrow
The bone marrow is central to leukemia because it is where many leukemias originate and where abnormal cells accumulate.
As leukemia cells crowd out healthy blood-forming cells, the body may produce fewer normal red blood cells, platelets, and functioning white blood cells. This can contribute to symptoms such as fatigue, infections, bruising, and bleeding.
Lymph nodes
Leukemia cells can accumulate in the lymph nodes, causing them to become enlarged. Enlarged lymph nodes may be noticed as painless lumps, particularly around the neck, underarms, or groin.
However, swollen lymph nodes do not necessarily mean leukemia; infections and many other conditions can cause the same finding.
Spleen
The spleen can become enlarged when leukemia cells accumulate there. An enlarged spleen may cause a feeling of fullness or discomfort in the upper left side of the abdomen. Some people may feel full after eating only a small amount because an enlarged spleen can press against the stomach.
Liver
Leukemia cells can also accumulate in the liver, potentially causing it to become enlarged. Liver involvement may not cause obvious symptoms by itself. When the liver becomes enlarged, however, some people may experience abdominal discomfort or a feeling of fullness.
Brain and spinal cord
Certain leukemias, particularly some forms of acute lymphoblastic leukemia (ALL), can involve the central nervous system, which includes the brain and spinal cord.
Because of this possibility, doctors may perform specific tests to determine whether leukemia cells are present in the fluid surrounding the brain and spinal cord when clinically appropriate.
Symptoms suggesting nervous-system involvement can vary and may include headaches, vomiting, changes in vision, weakness, seizures, or other neurological symptoms. These symptoms can have many causes and require medical evaluation rather than being assumed to indicate leukemia.
Skin and other tissues
Some types of leukemia can affect the skin or other tissues outside the bone marrow and blood. For example, AML can sometimes spread outside the blood to areas including the skin, gums, lymph nodes, spleen, liver, and central nervous system. The pattern of involvement depends on the specific leukemia subtype and its biological characteristics.
Does the Spleen or Liver Become Affected Before the Bone Marrow?
Generally, no. For most leukemias, the disease originates in the blood-forming system, particularly the bone marrow, rather than beginning in the spleen or liver.
If leukemia cells are later found in the spleen or liver, this represents involvement of those organs by the leukemia. It does not mean that the cancer originally started there.
This distinction is important because leukemia is fundamentally different from a cancer that originates in an organ such as the liver and then spreads elsewhere.
Why Does the Spleen Become Enlarged in Leukemia?
The spleen filters blood and plays an important role in the immune system. Because leukemia cells circulate through the blood, abnormal cells can accumulate in the spleen.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
This can cause the spleen to become enlarged, a condition called splenomegaly. An enlarged spleen may cause:
- Fullness or discomfort in the upper left abdomen
- Feeling full quickly after eating
- Abdominal pressure
- Occasionally, pain or discomfort that extends toward the left shoulder
Does Leukemia Always Affect Other Organs?
No. Leukemia does not necessarily involve every organ listed above. Some patients may have disease primarily involving the bone marrow and blood, while others may have involvement of lymph nodes, the spleen, liver, central nervous system, skin, or other tissues.
The pattern depends on the type and subtype of leukemia, the biology of the abnormal cells, and the individual disease course.
For example, CLL commonly involves the blood and bone marrow but can also involve the lymph nodes, liver, and spleen. ALL can involve the lymph nodes, spleen, liver, central nervous system, and testicles. AML can also spread outside the blood and bone marrow to several tissues.
What Symptoms Can Occur When Leukemia Affects Different Areas?
The symptoms of leukemia often result from the effect of abnormal cells on normal blood production rather than from one specific organ.
| Area affected | Possible symptoms or findings |
|---|---|
| Bone marrow and blood | Fatigue, anemia, infections, bruising or bleeding, abnormal blood counts |
| Lymph nodes | Painless swelling or lumps, particularly in the neck, underarms, or groin |
| Spleen | Upper abdominal fullness, discomfort, feeling full quickly |
| Liver | Abdominal fullness or enlargement of the liver |
| Central nervous system | Headache, vomiting, neurological or visual symptoms in some cases |
| Skin | Skin lesions or other changes in certain leukemia subtypes |
These symptoms are not specific to leukemia. Many other medical conditions can cause them, so diagnosis requires appropriate blood tests and, when necessary, examination of the bone marrow or other tissues.
How Do Doctors Find Out Which Parts of the Body Are Affected?
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The evaluation depends on the leukemia type and the patient's symptoms. Doctors may use several investigations to understand the extent of disease.
Blood tests
A complete blood count (CBC) can identify abnormalities in red blood cells, white blood cells, and platelets. A peripheral blood smear may also help identify abnormal blood cells.
Bone marrow examination
A bone marrow aspiration and biopsy can help confirm the diagnosis, identify the leukemia subtype, and assess the characteristics of the abnormal cells.
Imaging tests
Imaging may be used when doctors need to evaluate enlarged lymph nodes, the spleen, liver, or other areas of the body.
Specialized testing
Depending on the suspected leukemia, doctors may also use flow cytometry, chromosome testing, molecular tests, or other laboratory investigations. These tests can help establish the exact leukemia subtype and identify characteristics that influence treatment.
Testing for central nervous system involvement
For leukemia types in which the central nervous system may be involved, doctors may perform a lumbar puncture to examine cerebrospinal fluid for leukemia cells.
Does Organ Involvement Mean Leukemia Is Advanced?
Not necessarily. The significance of involvement outside the bone marrow and blood depends on the leukemia subtype. Unlike many solid cancers, leukemia is not generally described using a universal Stage I–IV system.
For some leukemias, doctors instead consider whether the disease is newly diagnosed, in remission, recurrent, or resistant to treatment. Other leukemia types have their own disease-specific staging or classification systems.
Therefore, finding leukemia cells in an organ does not automatically mean that the disease has reached a particular “stage.” The meaning has to be interpreted in the context of the specific leukemia.
The Bottom Line
Leukemia generally does not begin in an organ such as the liver or spleen. It is a cancer of the blood-forming system, with the bone marrow being the primary site involved in many forms of leukemia.
As abnormal leukemia cells enter the bloodstream and accumulate, they can affect the lymph nodes, spleen, liver, central nervous system, skin, and other tissues. The organs involved and the significance of that involvement depend on the specific type and subtype of leukemia.
Most importantly, organ involvement should not be interpreted on its own as proof that leukemia is advanced or at a particular stage. Doctors use the leukemia subtype, blood and bone marrow findings, molecular characteristics, disease status, and other clinical information to understand the disease and determine the appropriate treatment approach.
