What Is Chronic Lymphocytic Leukemia?
Lymphocytes work for the immune system, so this cancer affects health in more ways than one.

“Chronic lymphocytic leukemia is the most common type of leukemia in the United States,” says Sangmin Lee, MD, hematologist-oncologist at Weill Cornell Medicine and NewYork-Presbyterian. Like other types of leukemia, chronic lymphocytic leukemia (CLL) begins in the stem cells of the bone marrow.
Let’s put this into context: The types of leukemia depend on which early blood cells are affected (the myeloids or the lymphocytes) and how quickly the cancer is progressing (acute or chronic). The four main types of leukemia include:
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Acute lymphocytic leukemia
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Chronic lymphocytic leukemia
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Acute myeloid leukemia
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Chronic myeloid leukemia
The lymphocytes are a type of white blood cell, and as the name suggests, they also affect the lymph nodes. “Your lymphoid [stem cells] originate from your bone marrow, and then mature and migrate into the lymph nodes,” says Dr. Lee. That’s why a common symptom of CLL is enlarged lymph nodes.
Compared to an acute type of leukemia, CLL progresses more slowly, is less likely to cause symptoms, and is less likely to require immediate and aggressive treatment. Here are more differences between acute and chronic leukemia.
Lymphocytes are part of the immune system. Like all blood cells, they’re made in the bone marrow, and once mature, they enter the bloodstream, where they help make antibodies, fight pathogens, and help control the immune response, according to the National Cancer Institute.
There are two types of lymphocytes: B cell lymphocytes and T cell lymphocytes. In most cases, CLL specifically affects the B cell lymphocytes (which help produce antibodies to defend against illness).
However, in an individual with CLL, the leukemia cells multiply faster than normal and healthy lymphocytes. Leukemia cells cannot fully mature, and they cannot perform the same functions as healthy lymphocytes. As a result, the leukemia cells begin to crowd out the healthy cells and inhibit the role of B lymphocytes in the body.
Once leukemia cells enter the bloodstream, they commonly spread to other organs, such as the lymph nodes and the spleen. The lymph nodes are small, bean-shaped organs throughout the body that contain lymphocytes to fight infections and illnesses. Lymph nodes are located in clusters in the neck, underarm, chest, abdomen, and groin, according to the National Cancer Institute.
“Sometimes, the only presenting symptom can be an elevated white blood cell [count] in your blood report,” says Dr. Lee. In fact, most of those are leukemia cells that are ineffective against diseases. This can make individuals with CLL vulnerable to infections.
According to Dr. Lee, other symptoms may include:
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Enlarged lymph nodes
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Fever
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Chills
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Unintended weight loss
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Enlarged spleen
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And a sense of fullness.
CLL vs. Small Lymphocytic Lymphoma
Leukemia and lymphoma are different types of blood cancer, but there are so many similarities between chronic lymphocytic leukemia and small lymphocytic lymphoma (SLL) that they are often considered the same disease.
Both CLL and SLL affect the B cell lymphocytes, so once they progress, they often present the same problems and are treated similarly. There’s one key difference: When the bulk of the cancer cells are in the bloodstream and bone marrow, doctors diagnose it as CLL; when they’re mostly in the lymph nodes—and hardly in the bloodstream—it’s diagnosed as SLL, according to the Lymphoma Research Foundation.
“Knowing exactly what kind of leukemia you have is extremely important for treatment purposes and for prognosis,” says Dr. Lee.
Dr. Lee is a hematologist-oncologist at Weill Cornell Medicine and NewYork Presbyterian.
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Chronic lymphocytic leukemia is
the most common type of leukemia in
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the United States.
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Chronic lymphocytic leukemia affects
the lymphoid stem cells that can be found
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in your bone marrow as
well as your lymph nodes.
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Chronic lymphocytic leukemia, you may have
no symptoms or you may have symptoms.
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Sometimes the only presenting symptom can
be an elevated white blood cell in your
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blood report.
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And typically your lymphocytic cells and
your white blood cell would be elevated in
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certain types of chronic
lymphocytic leukemia.
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One common presenting symptom of chronic
lymphocytic leukemia is enlarged
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lymph nodes.
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But any leukemia can involve
your immune system, so
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you may be at more risk
of obtaining infections.
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And also your ability to fight
infection may be impaired.
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You may have fever, chills,
or unintended weight loss.
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One other presenting symptom of chronic
lymphocytic leukemia is that it can
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involve the spleen.
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If your spleen is enlarged then
your abdomen may feel more full.
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Chronic lymphocytic leukemia
is not always treated.
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You may not need treatment,
but just observations.
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Reason for a treatment would be if you
have decrease in some of your blood count
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such as hemoglobin or platelets.
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Or your lymph nodes are really enlarged,
then that requires treatment.
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Until recently,
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chemotherapy used to be how chronic
lymphocytic leukemia has been treated.
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But there are drugs that are more
targeted towards the CLL, and
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you may not require conventional
chemotherapy but more targeted therapy.
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We also have many clinical studies, where
many novel therapies are being tested that
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may actually be very promising for
treatment of chronic lymphocytic leukemia.
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Of course having a diagnosis of leukemia
is not easy, but chronic lymphocytic
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leukemia is a disease where you may
live a very long time without treatment.
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And even if you do need treatment,
treatment is improving every day for
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this type of leukemia.
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And patients may have an extended lifespan
much longer than what they had previously,
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because of the new developments in
treatment of chronic lymphocytic leukemia.
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Chronic lymphocytic leukemia/small lymphocytic lymphoma. New York, NY: Lymphoma Research Foundation, 2018. (Accessed on December 28, 2021 at https://www.lymphoma.org/aboutlymphoma/cll/.)
Chronic lymphocytic leukemia/small lymphocytic lymphoma fact sheet. New York, NY: Lymphoma Research Foundation, 2018. (Accessed on December 28, 2021 at https://www.lymphoma.org/wp-content/uploads/2018/04/LRF_FACTSHEET_CLL_SLL.pdf.)
Definition of chronic lymphocytic leukemia/small lymphocytic lymphoma. Bethesda, MD: National Cancer Institute. (Accessed on December 28, 2021 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/chronic-lymphocytic-leukemia-small-lymphocytic-lymphoma)
Definition of lymph node. Bethesda, MD: National Cancer Institute. (Accessed on December 28, 2021 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/lymph-node?redirect=true.)
Definition of lymphocyte. Bethesda, MD: National Cancer Institute. (Accessed on December 28, 2021 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/lymphocyte.)
Definition of white blood cell. Bethesda, MD: National Cancer Institute. (Accessed on December 28, 2021 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/white-blood-cell.)
What is chronic lymphocytic leukemia? Atlanta, GA: American Cancer Society, 2018. (Accessed on December 28, 2021 at https://www.cancer.org/cancer/chronic-lymphocytic-leukemia/about/what-is-cll.html.)