Leukemias
Chronic lymphocytic leukemia (CLL/SLL)
Also called Chronic lymphocytic leukemia/small lymphocytic lymphoma
If you or someone you love has just heard this diagnosis, start here. This guide explains what the condition is, how it is usually treated and whether a transplant plays any part.
Chronic lymphocytic leukemia and small lymphocytic lymphoma (CLL/SLL) are two presentations of the same mature B-cell cancer. Many people initially need monitoring; targeted medicines are the usual treatment, and donor transplantation is reserved for selected difficult-to-treat disease.
Other names and abbreviations
CLL/SLL, CLL, SLL, leukemia, CLL and SLL are blood/marrow- and nodal-predominant presentations of one entity
In short
- CLL and small lymphocytic lymphoma (SLL) are two forms of the same B-cell cancer. CLL is found mostly in the blood, and SLL mostly in the lymph nodes.
- Many people are watched closely at first. When treatment is needed, it is usually targeted medicine, often with an antibody drug.
- A donor transplant is uncommon and saved for some hard-to-treat cases. So most people with CLL or SLL do not need a donor.
Jump to a section
Underlined words open a short explanation. See all terms
Where transplant fits
Allogeneic transplantationComing from another person. In an allogeneic, or donor, transplant, the stem cells come from a relative or an unrelated volunteer whose cells are a close enough match to the patient's. is uncommon and reserved for selected difficult-to-treat CLL/SLL or aggressive transformation. Usual targeted treatmentMedicines designed to act on specific molecules involved in a disease. In cancer, they target molecules that cancer cells need to survive and spread. Some block signals that tell cancer cells to grow; others help the immune system kill them. and approved autologousComing from the patient's own body. In an autologous transplant, the patient's own stem cells are collected and stored, then given back after high-dose treatment. It does not use a donor. CAR-T therapyA treatment that takes a patient's own T cells, changes them in a lab so they can find and attack cancer cells, then gives them back through a vein. Standard CAR-T therapy does not use a donor. do not use registry donor cells.
Treatment depends on the exact diagnosis, disease stage, prior treatment and the person’s health.
Key facts
- Who it affects
- CLL/SLL mainly affects older adults and is uncommon in children.
- How common
- About 22,760 new cases in 2026 (estimated)Estimated new CLL diagnoses in the United States, 2026 (SEER); about 5 in 100,000 people each year, age-adjusted, 2019 to 2023; median age at diagnosis 71 Source: How common
- Cells used in a transplant
- Donated blood-forming cells for allogeneic transplantation. Marrow, peripheral blood or cord blood and donor type are selected for the patient and transplant approach.
- Where a donor fits
- Limited transplant role
The condition
What it is
CLL and SLL involve the same kind of abnormal B lymphocyteA type of white blood cell that makes antibodies. B cells are part of the immune system and grow from stem cells in the bone marrow. Some lymphomas and leukemias start in B cells.. The name largely depends on where the cells are found: CLL has a characteristic number in blood, while SLL is mainly in lymph nodes or other tissues.
This cancer usually affects older adults and often develops slowly. Blood tests, examination and sometimes a tissue biopsy establish the diagnosis. Before treatment, testing such as TP53 analysis, chromosome studies and IGHV mutation status helps guide the choice of medicines.
Marked as affected: B cells.
- Blood stem cell, In the bone marrow
- Myeloid line
- Red blood cells
- Platelets
- Granulocytes
- Monocytes
- Lymphoid line
- B cells, Affected
- Plasma cells, Develop from B cells
- T cells
- NK cells, Natural killer cells
- Myeloid line
What causes it
CLL/SLL arises when B cells acquire changes that allow them to survive and accumulate. Its cause is often unknown. Risk can run in families, but most cases are not explained by a simple inherited gene change.
The abnormal cells do not provide normal immune protection. CLL/SLL is not contagious, and finding a chromosome or gene abnormality in the cancer does not itself show an inherited condition.
Symptoms and effects
Some people feel well and discover CLL through a blood test. Others have swollen lymph nodes, fatigue, night sweats, weight loss or an enlarged spleen. Low blood counts can result from marrowThe soft, spongy tissue in the center of most bones. Red bone marrow holds the blood-forming stem cells that make red blood cells, white blood cells and platelets. involvement or immune destruction of blood cells.
Infection risk may increase even when treatment has not started. A small proportion of cases transform into a more aggressive lymphoma, often called Richter transformation. Rapidly changing symptoms or lymph-node growth need clinical reassessment rather than an assumption that this is ordinary CLL progression.
A simple drawing of a body. Can be affected: liver, spleen, bone marrow and lymph nodes.
Can be affected
- Liver
- Spleen
- Bone marrow
- Lymph nodes
This shows the parts of the body the condition can affect. Most people have only some of these, and the drawing says nothing about how severe any of them will be.
Diagnosis and treatment
How CLL and SLL are diagnosed
CLL may first be found on a routine blood test, before any symptoms. Flow cytometry, a lab test that reads the markers on the cells, is key to the diagnosis. In CLL, the blood lymphocyte count is usually 5,000 or more per microliter. The cells carry a typical set of markers, including CD5, CD19, CD20 and CD23.
SLL is the same disease found mainly in the lymph nodes. A lymph node biopsy may be done when blood tests are not enough to make the diagnosis, or when a node has grown very large. A bone marrow biopsy is usually not needed. A CT scan is usually not needed unless the lymph nodes are enlarged.
Before treatment starts, more tests help choose the medicine. FISH looks for chromosome changes, such as a missing piece of chromosome 17 (del(17p)). Gene tests check TP53 and whether the IGHV gene is mutated. NCI's list of tests also includes antibodyA protein made by the immune system that sticks to one specific target, such as a germ. Some wrongly target the body's own tissues. Lab-made antibody medicines can target markers such as CD20 or CD38 on some cancer cells. (immunoglobulin) levels and tests for hepatitis B, hepatitis C and HIV.
A small group of these cells in the blood, fewer than 5,000 per microliter, with no enlarged lymph nodes or spleen, is called monoclonal B-cell lymphocytosis (MBL), not CLL. NCI cites studies that found MBL in 3 in 100 adults over 40. Low-count MBL rarely turns into CLL.
How it is treated
Asymptomatic disease that does not meet treatment criteria is often actively monitored. Starting treatment simply because CLL cells are present does not benefit everyone; the team watches symptoms, blood counts and the pace of change.
When treatment is needed, options include BTK inhibitors and venetoclax-based combinations, often with an anti-CD20 antibody. The choice and duration depend on disease genetics, previous treatment, other health conditions and patient preferences. CAR-T therapy and clinical trialsA research study that tests how well a new medical approach works in people. Trials can test new ways to screen for, prevent, diagnose or treat a disease. are options for selected previously treated patients.
Allogeneic transplantation is uncommon and generally considered after resistance to important targeted-treatment classes or in selected aggressive transformation. It can produce durable disease control but carries substantial risks. Autologous transplantation is not standard treatment for CLL itself.
Kinds of treatment described for chronic lymphocytic leukemia (CLL/SLL): watching and regular checks, medicines, a donor stem cell transplant (for a few people) and CAR T-cell therapy (for some people).
After diagnosis, the options described here
Watching and regular checks
CLL without symptoms that does not meet treatment criteria is often watched, with the team tracking symptoms and blood counts.
Medicines
Targeted medicines such as BTK inhibitors or venetoclax-based combinations, often with an antibody drug.
Donor stem cell transplant, For a few people
Generally considered only when CLL resists the main targeted medicines or turns into a more aggressive lymphoma.
CAR T-cell therapy, For some people
Approved for some people treated before, CAR-T uses the person’s own changed T cells, not a donor’s.
These are the kinds of treatment this page describes, not a plan. Which ones fit, in what order and whether they are combined differs from person to person.
When transplant specialists are usually consulted
NMDP guidelines suggest a transplant consultation when CLL stops responding to both main types of targeted medicine (BTK inhibitors and BCL2 inhibitors), or when their side effects cannot be tolerated. They also suggest one when CLL changes into a fast-growing lymphoma (Richter transformation).
Read the guidanceDaily life and the donor’s role
Living with the condition and treatment
Active monitoring still means living with a diagnosis and attending follow-up. Some people want help understanding which changes matter and how often tests are planned. Treatment may be continuous or time-limited, depending on the regimen.
Infection prevention, vaccines appropriate to the person’s immune status and attention to other cancers are part of care. CLL and some of its treatments weaken the body’s defenses against infection, so finding and treating infections early is important. Drug-specific monitoring may include bleeding risk, heart rhythm, interactions or tumor lysis precautions.
The role of a blood stem cell donor
Most people with CLL/SLL do not need a registry donor. A donor is relevant only if allogeneic transplantation is chosen for a particular clinical situation.
If it is chosen, the team assesses relatives, unrelated donors and appropriate alternative graftsThe blood-forming stem cells given to a patient in a transplant. In a donor transplant, the graft comes from the donor's bone marrow or blood, or from donated cord blood.. CAR-T treatment is different: the usual products use the patient’s own modified T cellsA type of white blood cell that is part of the immune system. T cells grow from stem cells in the bone marrow, help protect the body from infection and may help fight cancer., not cells from a registry donor.
Looking ahead
Looking ahead
Outlook for CLL and SLL
Through the 1990s, half of people with CLL lived longer than 8 to 12 years. Since targeted medicines arrived, NCI notes that more than half are still alive after over 10 years of follow-up.
Several things shape the outlook. One is the stage, which reflects the lymph nodes, spleen, liver and blood counts. Another is the leukemia's genes. A mutated IGHV gene is linked with longer survival, and an unmutated one with shorter survival. A missing piece of chromosome 17, or a TP53 change, is linked with poorer response to standard treatment and the least favorable outlook. Older age matters too. NCI notes that risk scores built before today's medicines may need to be rechecked.
In about 2 to 10 in every 100 people, CLL changes into a fast-growing lymphoma (Richter transformation). This changes the outlook. It is also one of the situations in which NMDP guidelines suggest a transplantA treatment that gives a patient healthy blood-forming stem cells through a vein. The cells travel to the bone marrow and replace faulty marrow or marrow damaged by treatment. They can come from the patient or a donor. consultation.
About these numbers. Each one says which group of people it comes from, and the place and years where the source gives them. It describes what happened across that group, not what will happen to any one person. And a figure measured among people who had a transplant is not the same as the number of people who need one.
- 90.2%5-year relative survival
People of all ages diagnosed with CLL in U.S. SEER 21 areas (excluding Illinois), 2016 to 2022
Read the source: 5-year relative survival
Group figures cannot predict how one person will do, and many people with CLL are older and have other health conditions.
Common questions
Is CLL curable?
In most cases, CLL is controlled rather than cured. NCI's summary for health professionals says treatment for progressing CLL will not be curative in most cases. Many people start with watchful waiting, which means close monitoring without treatment, and targeted medicines are used when treatment is needed. In selected patients, a donor stem cell transplant has led to long disease-free periods, sometimes more than 20 years, but few people with CLL need one.
What is the survival rate for CLL?
In the United States, most people with CLL are alive five years after diagnosis. CLL often develops slowly, but its course differs from person to person. The outlook section on this page gives the figures, with the groups they describe. Group numbers cannot predict any one person's outcome.
What is the difference between CLL and SLL?
CLL and SLL are different forms of the same slow-growing cancer of B lymphocytes, a type of white blood cell. The name depends mostly on where most of the cancer cells are. It is called CLL when they are mainly in the blood and bone marrow, and SLL when they are mainly in the lymph nodes and spleen. Because they are so closely related, doctors often write it as CLL/SLL.
Why is CLL often watched instead of treated right away?
CLL often causes no symptoms at first, and starting treatment just because CLL cells are present does not help everyone. NCI's professional summary notes that trials found no survival benefit from treating early-stage disease right away rather than later. So the care team often monitors symptoms, blood counts and how fast things change, and starts treatment when specific signs show it is needed.
Does CLL need a bone marrow transplant?
Rarely. Most people with CLL/SLL never need a registry donor. When treatment is needed, targeted medicines are the usual choice. A donor stem cell transplant is generally considered only when the disease resists, or cannot be treated with, the main targeted medicines (BTK and BCL2 inhibitors), or when it turns into a more aggressive lymphoma. CAR-T therapy, approved for some previously treated patients, uses the patient's own cells, not a donor's.
What are the first signs of CLL?
Many people feel well and learn they have CLL from a routine blood test. Others notice swollen lymph nodes, tiredness, fever, night sweats, weight loss, or a full feeling in the belly from an enlarged spleen or liver. As CLL advances, low blood counts can make infections, bruising and bleeding more likely. Blood tests that show too many lymphocytes are the main way CLL is found and diagnosed.
For your next appointment
Chronic lymphocytic leukemia (CLL/SLL)
From the Jada Bascom Foundation disease library, jadabascomfoundation.org. Printed .
Questions to bring to your care team
- What did the FISH, TP53 and IGHV tests show, and how do they affect treatment choices?
- What changes in blood counts, lymph nodes or symptoms would mean it is time to start treatment?
- Is the suggested treatment taken for a set time or ongoing, and what side effects will you watch for?
- Which vaccines and infection precautions make sense, and what signs of Richter transformation should we report?
- What is the exact name of the diagnosis or subtype, and what does it mean for treatment?
- What is the goal of each treatment you are suggesting?
- What would make a transplant worth considering later on?
- Are there clinical trials that might fit?
- Where can our family find support during treatment?
A one-page list to take to the next appointment, with room for notes.
Supporting someone with a diagnosisSupport for patients and families
These independent organizations offer information and support. JBF is not affiliated with them.
- CLL Society US nonprofit for people with CLL and SLL, offering education, support groups, one-on-one support and resources for care partners.United States
- Lymphoma Action UK charity for people affected by lymphoma, with a free helpline, support meetings and peer buddies; it covers CLL and SLL.United Kingdom
- Lymphoma Research Foundation US nonprofit devoted to lymphoma; it explains CLL/SLL and runs a helpline for questions from patients and families.United States
Sources and further reading
- Chronic Lymphocytic Leukemia Treatment (PDQ), Health Professional Version
NCI, Accessed 2026-09-05 - Indications for haematopoietic cell transplantation and CAR-T: 2025 EBMT practice recommendations
EBMT / Bone Marrow Transplantation, Accessed 2026-09-05 - Stem Cell and Bone Marrow Transplants for Cancer
NCI, Accessed 2026-09-05 - Donor and cord blood unit selection guidelines
NMDP / CIBMTR, Accessed 2026-09-05 - Chronic Lymphocytic Leukemia Treatment (PDQ), Patient Version
National Cancer Institute, Accessed 2026-09-24 - Chronic lymphocytic leukemia (CLL) — HCT consultation timing guidelines
NMDP, Accessed 2026-09-24 - Chronic Lymphocytic Leukemia — Cancer Stat Facts
National Cancer Institute, SEER Program, Accessed 2026-09-24 - What Is Chronic Lymphocytic Leukemia?
American Cancer Society, Accessed 2026-09-24 - BREYANZI (lisocabtagene maraleucel)
US Food and Drug Administration, Accessed 2026-09-24 - Signs and Symptoms of Chronic Lymphocytic Leukemia
American Cancer Society, Accessed 2026-09-24 - Tests for Chronic Lymphocytic Leukemia
American Cancer Society, Revised 2025-03-20; accessed 2026-09-26
This information explains a condition and its treatments. It cannot diagnose an illness or recommend treatment for an individual. Your care team can explain how the evidence applies to you. Written and source-checked by the Jada Bascom Foundation. Each page lists the published sources it draws on.
Ways to help
Help another family understand.
Most people with chronic lymphocytic leukemia (CLL/SLL) are treated without a registry donor. A clear explanation can help the next family who hears this diagnosis, and many people with other blood cancers and blood disorders need a donor who is a stranger.
Learn and share
Most families meet these words for the first time at a diagnosis. Passing on a plain, sourced explanation is a real help.
Support this work
Gifts to the Jada Bascom Foundation support donor-awareness education like this page, community outreach, drive planning and referrals to official registries.
Join the registry
JBF points you to the official registry that serves your country. It explains who can join and what donation involves.
More in the library
Keep learning
Interactive storyWhy matching is hard: leukemiaHow leukemia affects blood production, when a donor transplant may help, and how inherited HLA markers shape the search for a suitable donor.Begin the storyPart of 4 diagnosis guides, each explaining how its subtypes fit together: Leukemia, Non-Hodgkin lymphoma (NHL), Lymphoma and Types of blood cancer.
