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Small lymphocytic lymphoma

What is SLL?

SLL (small lymphocytic lymphoma) is an indolent (slow growing) non-Hodgkin lymphoma that affects B cells.

B cells (also known as B lymphocytes) are specialised white blood cells. Under normal conditions they produce immunoglobulins (also called antibodies) that help protect our bodies against infection and disease.

The World Health Organisation (2016) classifies SLL and CLL (chronic lymphocytic leukaemia) as essentially the same disease. The difference between SLL and CLL is where the blood cancer is located. CLL has most of the cancerous B lymphocytes in the bloodstream (like a leukaemia), whereas SLL has most of the cancerous B lymphocytes in the lymph nodes and lymphoid tissue such as the spleen and the tonsils (like a lymphoma).

SLL and CLL can be coupled together and expressed as SLL/CLL.  Around 300 Australians will be diagnosed with SLL each year representing 5% of all lymphomas.

The first sign of SLL is usually a painless swelling in the neck, armpit or groin which is caused by enlarged lymph nodes due to infiltration of normal lymph nodes by the cancerous B-cells. Other symptoms of SLL may include night sweats, fevers and unexplained weight loss.

The cancerous B-cells usually appear normal under the microscope, but they are not fully developed and have specific proteins on the surface known as CD5 and CD19. These B-cells are immature cells and do not function properly as a result.

How does SLL/CLL affect the body?

SLL/ CLL that accumulates in the bone marrow and the spleen can deplete the amount of healthy blood cells in the circulating blood (blood that flows throughout the body). Due to lower red blood cells (anaemia) and low platelet numbers in the bloodstream (thrombocytopenia) fatigue, shortness of breath and a tendency to bruise or bleed may occur. These symptoms may require transfusions of red blood cells or platelets. This problem is referred to as bone marrow failure and is due to the normal bone marrow being over-run by cancerous B cells

Rare potential SLL/ CLL complications

Richter’s Syndrome/Transformation

Richter’s Syndrome (RS), also known as Richter’s Transformation, is a rare complication of SLL/ CLL which develops into a significantly more aggressive form of large cell lymphoma.

Although, SLL/ SLL are generally slow-growing blood cancers, in the small number of people who develop RS (2-10%), treatment will be similar to that given for aggressive B cell blood cancers.

You can read more about Richter’s Syndrome (RS) on our website.

Haemolytic anaemia and Immune thrombocytopaenic purpura

SLL/CLL can inhibit the immune system and make fighting infections more difficult. It can also cause the immune system to attack itself which is known as autoimmunity. When this occurs, two life-threatening conditions may develop. When the immune system attacks red blood cells, a process referred to as auto-immune haemolytic anaemia (AIHA) occurs. Approximately 7% of patients with SLL/ CLL have AIHA at some stage.

When platelets (the clotting component in blood) are attacked by the immune system, immune thrombocytopenic purpura (ITP) occurs. AIHA and ITP may require urgent medical inpatient care which includes treatment of the underlying blood cancer.

Who does SLL/CLL affect?

SLL/CLL affects adults and is usually diagnosed in people aged over 60 years. The median age of people at diagnosis is 65 years and is more common in men than in women.

What causes SLL/CLL?

The causes of SLL/CLL are unknown. Doctors and researchers continually work to understand the exact mechanisms that cause this disease. It is not infectious and cannot be passed on to other people.

How is SLL/CLL treated?

Genetic testing for SLL/CLL is recommended prior to the treatment starting. This identifies any chromosomal abnormalities or specific gene mutations prior to treatment and is important to help your treatment team decide on the most appropriate treatment.

People who feel well and do not have any symptoms are usually managed by watch and wait (active observation only). This involves regular appointments with the treatment team who will monitor the person’s condition. Should symptoms develop, or the person becomes unwell, or large tumours or bone marrow failure occurs, treatment will need to be commenced.

Standard Drug Treatment

Your treatment team might use the term ‘standard of care’ or ‘standard therapy’. This is a treatment that is commonly used by medical experts for a certain type of disease.

Treatment for SLL may involve the use of low or high intensity combination chemotherapy, more recently with a targeted therapy such as a monoclonal antibody. This is commonly known as chemoimmunotherapy. The combination of drugs will depend on your age, stage of disease and risk factors. Your treatment team will consider these things and discuss the best treatment for you. These drugs are given in tablet form, injected under the skin or intravenously.

Targeted therapies

Monoclonal antibodies

Monoclonal antibodies work by helping a person’s own immune system to recognise cancerous cells as foreign and kill them.

Bruton Tyrosine Kinase (BTK) Inhibitors

Bruton Tyrosine Kinase (BTK) inhibitors are an evolving group of new drugs that inhibit the enzyme BTK. They help to trigger cell death by blocking the B-cell receptor signaling that leukemias and lymphomas use to grow and survive. SLL/ CLL use B-cell receptor signaling for growth and survival so blocking this pathway stops the blood cancer growing and surviving.

Supportive Care

Supportive care prevents and treats symptoms and side effects. It can also include emotional and social support. The goal is to improve symptoms of your SLL/ CLL, but it doesn’t treat the disease itself. People with stage B and C SLL/CLL may have supportive care alongside treatment.

This could include blood or platelet transfusions. Blood transfusions are a bag of red blood cells which are slowly given via your vein in a clinic or in an outpatient ward of a hospital. Platelets are like a red blood cell transfusion, but you will be given a bag of platelets instead of packed red blood cells.


Steroids are an important part of SLL/CLL treatment. They have many functions including the ability to improve blood counts of healthy cells and treat autoimmune problems.

Stem Cell Transplantation

A bone marrow or stem-cell transplant may be offered to some people with high risk or advanced disease following initial treatment.  Stem-cell transplants may be autologous (person’s own stem cells are used), or allogeneic (stem cells are from a donor). Allogeneic transplants in people with SLL/CLL have proven to be quite successful in terms of curing people with this disease but there are significant risks and side effects associated with such transplants, which is why they are usually only given to relatively young, fit people. Your treatment team will advise what is best for you.

Clinical Trials

New treatments for SLL and CLL are being researched all the time and people may be invited by their doctor to take part in a clinical trial to compare a new treatment against the best available standard treatment. Although SLL and CLL are currently considered incurable, there is continuing hope that new therapies will eventually provide the answer to treating these diseases. Involvement in clinical trials is pivotal to answering these questions.

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Last updated on May 22nd, 2024

Developed by the Leukaemia Foundation in consultation with people living with a blood cancer, Leukaemia Foundation support staff, haematology nursing staff and/or Australian clinical haematologists. This content is provided for information purposes only and we urge you to always seek advice from a registered health care professional for diagnosis, treatment and answers to your medical questions, including the suitability of a particular therapy, service, product or treatment in your circumstances. The Leukaemia Foundation shall not bear any liability for any person relying on the materials contained on this website.