Small lymphocytic lymphoma (SLL) is a slow-growing cancer of the immune system. It is typically manageable with treatment, but outlook can depend on a few factors.

SLL is one type of non-Hodgkin’s lymphoma, along with chronic lymphocytic leukemia (CLL). The two cancers have been designated as the same disease with the same treatment options. The only difference between each cancer is its location in the body.

CLL occurs when the cancer cells are found in the blood, while SLL occurs when they are found in the lymph nodes. CLL can progress to SLL as cancer cells grow and spread.

The National Cancer Institute reports that in 2024, doctors will diagnose about 20,700 new cases of CLL in the United States.

People with SLL may not have any obvious signs for many years. Some may not realize they have the disease.

The main symptom of SLL is a painless swelling in the neck, armpit, and groin. It’s caused by cancer cells building up inside the lymph nodes.

Other symptoms can include:

  • fatigue
  • unexpected weight loss
  • fever
  • night sweats
  • swollen, tender belly
  • feeling of fullness
  • shortness of breath
  • easy bruising
  • skin lesions

Loss of working cells can make it harder for the immune system to produce antibodies and fight off infection.

Doctors don’t know exactly what causes SLL. Lymphoma sometimes runs in families, although scientists haven’t pinpointed a single gene that causes it.

While this cancer is mostly seen in adults ages 70 and older, it can occur in adults as young as 30. However, it is rare in children.

Risk factors for developing SLL and CLL can include:

  • older age
  • family history
  • long-term exposure to certain pesticides
  • exposure to radon at home

You may also be at a higher risk of this cancer if you have worked on a farm due to long-term exposure to certain pesticides.

Doctors can diagnose SLL by taking a biopsy of an enlarged lymph node. You typically get local anesthesia to numb the area first. If the enlarged node is deep in your chest or belly, you may get general anesthesia to sleep through the procedure.

During a biopsy, the doctor removes part or all the affected lymph node. The sample then goes to a laboratory for testing.

Doctors may recognize signs of CLL on a peripheral blood smear. This blood test looks at the appearance, count, and shape of red and white blood cells and platelets.

Other tests used to diagnose SLL and CLL can include:

  • a physical exam to check for enlarged lymph nodes or a swollen spleen
  • blood tests
  • imaging tests such as a PET scan or CT scan
  • fluorescence in situ hybridization (FISH) test to detect chromosomal abnormalities
  • bone marrow aspiration and biopsy
  • flow cytometry, which analyzes blood cells for cell surface markers and detects circulating leukemia cells

Whether you receive a diagnosis of SLL can depend on the number of lymphocytes in the blood. For a diagnosis of SLL, the American Cancer Society (ACS) reports that you must have an enlarged lymph node or spleen with fewer than 5,000 monoclonal, or cancerous, lymphocytes per cubic millimeter in the blood.

The SLL stage describes how far your cancer has spread. Knowing the stage can help a doctor find the right treatment and predict your outlook.

SLL staging is based on the Ann Arbor staging system. Doctors assign the cancer one of four stage numbers based on:

  • how many lymph nodes contain cancer
  • where those lymph nodes are in your body
  • whether the affected lymph nodes are above, below, or on both sides of your diaphragm
  • whether the cancer has spread to other organs, such as your liver

Stage I and II SLL are considered early stage cancers. Stage 3 and 4 are advanced stage cancers.

  • Stage 1: Cancer cells are in only one area of lymph nodes.
  • Stage 2: Two or more groups of lymph nodes contain cancer cells, but they’re all on the same side of the diaphragm (either in the chest or belly).
  • Stage 3: Cancer is in lymph nodes both above and below the diaphragm, or in the spleen.
  • Stage 4: Cancer has spread to at least one other organ, such as the liver, lung, or bone marrow.

As this type of cancer grows so slowly, not everyone with SLL needs treatment right away.

If you don’t have symptoms, a doctor may recommend “watching and waiting.” This means that a doctor will monitor the cancer without treating you. However, if your cancer spreads or you develop symptoms, then you’ll need to start treatment.

Treatment for later stage SLL is the same as it is for CLL.

Treatment options can include:

  • Radiation therapy: Lymphoma that’s only in one lymph node may be treated with radiation therapy. Radiation uses high energy X-rays to destroy cancer cells.
  • Chemotherapy: Chemotherapy can be given orally or through intravenous (IV) administration. These drugs can target and destroy cancer cells. Doctors use chemotherapy drugs such as chlorambucil (Leukeran), fludarabine (Fludara), and bendamustine (Treanda).
  • Monoclonal antibodies: These drugs help your immune system find and destroy cancer cells. Monoclonal antibody drugs, such as rituximab (Rituxan, MabThera) or obinutuzumab (Gazyva), can sometimes be used in addition to chemotherapy.
  • Targeted therapy drugs: These drugs work by targeting specific proteins, such as Bruton’s tyrosine kinase (BTK inhibitors), which allows the lymphoma cells to grow, and BCL-2 (BCL2- inhibitors), a protein that helps extend the lifespan of these cells.
  • Supportive care: This type of treatment targets health problems that may be related to the cancer, such as viral or bacterial infections and low blood counts.
  • Stem cell transplant: Some people may receive a stem cell treatment to replenish bone marrow after high doses of chemotherapy. This can help prevent infections and let doctors use a stronger dose of chemotherapy to target cancer cells.

If the first treatment you try doesn’t work or it stops working, a doctor will repeat the same treatment or have you try a new form of therapy. You can also ask a doctor about enrolling in a clinical trial.

Clinical trials are studies that test new medications and drug combinations. They may provide additional treatment options for people who have not had the desired level of success with past treatments.

Many of the existing therapies used to treat cancer began as part of a clinical trial. Sometimes the program sponsor will cover the cost of treatment received as part of a clinical trial.

While placebos may sometimes be used in some phase 3 studies, they’re never used alone if there’s a treatment available that works.

If you are interested in participating in a clinical trial, you can search for trials you may be eligible for on the NIH National Cancer Institute website.

When you have SLL, your outlook will depend on the stage of your cancer and other variables, such as your age and general health. It’s typically a slow-growing cancer that can be managed with treatment.

However, SLL often comes back after it’s treated. Most people will need to go through a few rounds of treatment to keep their cancer under control. You may also have extended breaks in between when you do not require treatment.

New treatments may increase the chance that you’ll go into remission — meaning there is no sign of cancer in your body — for a longer amount of time. Clinical trials test other new therapies that might be even more effective.