Small lymphocytic leukemia (SLL) is a cancer of the immune system. It affects infection-fighting white blood cells called B-cells.

SLL is one type of non-Hodgkin lymphoma, along with chronic lymphocytic lymphoma (CLL). The two cancers are basically the same disease, and they're treated in the same way. The only difference is each cancer is located in a different part of the body.

In SLL, cancer cells are mainly in the lymph nodes. In CLL, most of the cancer cells are in the blood and bone marrow.

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 painless swelling in the neck, armpit, and groin. It’s caused by cancer cells building up inside the lymph nodes.

Other symptoms include:

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

Not everyone with SLL needs treatment right away. If you don’t have symptoms, your doctor might recommend “watching and waiting.” This means that your doctor will monitor the cancer but won’t treat you. However, if your cancer spreads or you develop symptoms, then you’ll start treatment.

Lymphoma that’s only in one lymph node may be treated with radiation therapy. Radiation uses high-energy X-rays to kill cancer cells.

Treatment for later-stage SLL is the same as it is for CLL. Doctors use chemotherapy drugs such as chlorambucil (Leukeran), fludarabine (Fludara), and bendamustine (Treanda).

Sometimes chemotherapy is combined with a monoclonal antibody drug such as rituximab (Rituxan, MabThera) or obinutuzumab (Gazyva). These drugs help your immune system find and destroy cancer cells.

If the first treatment you try doesn’t work or it stops working, your doctor will repeat the same treatment or have you try a new drug. You can also ask your doctor about enrolling in a clinical trial. These studies test new medicines and drug combinations for SLL.

SLL/CLL is the most common form of leukemia among adults in the United States, making up 37 percent of cases.

In 2019, doctors will diagnose about 20,720 new U.S. cases of SLL/CLL. Each person’s lifetime risk of getting SLL/CLL is 1 in 175.

Doctors don’t know exactly what causes SLL and CLL. Lymphoma sometimes runs in families, although scientists haven’t pinpointed a single gene that causes it. If you have a family member with SLL, your risk of getting this cancer is still small overall.

Evidence suggests you might be at slightly higher risk of SLL/CLL if you’ve worked on a farm or as a hair stylist. Sun exposure may reduce your risk, but UV radiation from the sun is linked to other health problems, such as skin cancer.

Doctors diagnose SLL by taking a biopsy of an enlarged lymph node. You’ll 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 of the affected lymph node. The sample then goes to a laboratory for testing.

Other tests used to diagnose SLL include:

  • a physical exam to check for enlarged lymph nodes or a swollen spleen
  • blood tests
  • imaging tests such as an X-ray or CT scan

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

SLL staging is based on the Ann Arbor 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 III and IV 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, and/or is in the spleen.
  • Stage 4: Cancer has spread to at least one other organ, such as the liver, lung, or bone marrow.

When you have SLL, your outlook will depend on the stage of your cancer and other variables. It's generally a slow-growing cancer. Although it isn’t curable, it is manageable with treatment.

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.

New treatments are increasing 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 are testing other new therapies that might be even more effective.