Small lymphocytic lymphoma, or SLL, is a slow-growing type of non-Hodgkin lymphoma. If a person has this type of cancer, immature white blood cells are found mainly in the lymph nodes.

Chronic lymphocytic leukemia (CLL) and SLL are terms for the same disease, but CLL affects the blood and bone marrow instead of the lymph nodes. CLL and SLL cause similar symptoms and have similar treatment options.

CLL is the most common type of adult leukemia in Western countries. SLL accounts for 7% of new cases of non-Hodgkin lymphoma.

This article discusses the symptoms and treatment of SLL leukemia and compares it with CLL.

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SLL and CLL are both lymphocytic conditions that affect the immune system. However, they affect different areas of the immune system.

Both conditions are types of non-Hodgkin lymphoma. These cancers start in the white blood cells and affect the lymphatic system.

SLL: Lymph nodes

In people with SLL, cancer cells appear mainly in the lymph nodes.

The lymph nodes are small bean-shaped glands that contain white blood cells, or lymphocytes, and help filter substances that travel through the lymphatic fluid. Lymph nodes are part of the body’s immune system.

CLL: Bone marrow and blood cells

CLL also affects the immune system. However, in CLL, the cancer cells appear mainly in the bone marrow and blood cells. Bone marrow is the spongy tissue in the middle of the bones that makes substances that produce blood cells.

Cellular differences

When doctors examine the cancer cells under a microscope, both SLL and CLL look the same. However, there are some differences in the blood.

A person with CLL will have more than 5,000 monoclonal lymphocytes per cubic millimeter (mm³) in the blood. A person with SLL will have less than 5,000 monoclonal lymphocytes per mm³ in the blood, but they will also have a swollen spleen or swollen glands.

As the cancers are so similar, doctors use the same treatments for both SLL and CLL.

Learn more about slow-growing lymphoma here.

SLL is slow growing. It may not cause any symptoms at all for years. If a person is asymptomatic, they may be unaware that they have SLL.

When the cancer begins to cause symptoms, it mainly causes swollen lymph nodes in the neck, groin, and armpits.

In addition to swollen glands, a person with SLL may have the following symptoms:

Additionally, people with SLL have a higher chance of developing infections than those who do not have it. A person with SLL may notice frequent colds, cold sores, and more severe infections, such as pneumonia.

Learn about how leukemia affects the body here.

There are many treatment options for SLL.

Doctors determine a person’s treatment plan based largely on the symptoms they have. According to the Lymphoma Research Foundation, a person only needs treatment if they show symptoms or testing shows the cancer is worsening.

If a person has SLL but no symptoms, a doctor may decide that the best course of action is to monitor them and wait until their symptoms worsen before prescribing further treatment.

If a doctor determines a person needs treatment, the type of treatment will depend on the following factors:

  • age
  • health aside from SLL
  • stage of SLL
  • symptoms and severity
  • red and white blood cell counts
  • platelet levels
  • genetic mutations

Treatment options

Treatment options may include:

  • Immunotherapy: A person receives drugs that help boost their body’s immune system against the leukemia.
  • A combination of chemotherapy and immunotherapy: Doctors rarely use chemotherapy by itself to treat CLL or SLL.
  • Targeted therapy: This type of treatment may involve taking a pill orally. This medication will cause less harm to noncancerous cells.
  • Stem cell transplants: A person receives an injection of stem cells, which help form blood cells. This can help the recovery of people who have undergone aggressive treatment.
  • Clinical trials of new treatments: There are many new and promising treatment options that are not currently approved. A person can discuss the pros and cons of clinical trials for their unique situation with their doctor.
  • Chimeric antigen receptor (CAR) T cell therapy: This type of treatment is currently available through clinical trials. It involves removing some immune cells, called T cells, from a person’s blood. Doctors then modify the cells so they can fight the cancer, before reinjecting them into the person’s veins.

SLL leukemia is a type of slow-growing cancer, which means a person may not experience symptoms or require treatment for years.

According to the National Cancer Institute, the 5-year survival rate for CLL and SLL is 86.9%. The 5-year survival rate has improved by more than 20% since 1975 thanks to improvements in treatment and detection.

Learn about the outlook for CLL here.

According to the American Cancer Society, scientists do not yet know exactly what causes most cases of SLL. However, they do know that there are differences between healthy lymphocytes and SLL cells. They think the cancer triggers when lymphocytes divide uncontrollably after contact with a foreign substance, such as a germ.

DNA and genetic mutations that affect genes that promote cell division and growth, and mutations in genes that slow down cell division, may also play a role in SLL. While a person can inherit these mutations, most of the changes related to SLL happen during a person’s lifetime.

In most cases of SLL, there is a change found in one of the 23 pairs of chromosomes in the human cells. Normally, part of the chromosome is deleted or lost. The deletion of part of chromosome 13 is the most common, but parts of other chromosomes may be deleted as well.

Sometimes, there is an extra chromosome (trisomy) or another mutation that plays a role in the development of SLL. While scientists know these changes and mutations impact SLL, they are not yet entirely sure how.

Some people may receive a diagnosis of SLL when a doctor does routine blood work during their yearly checkup. These people are generally asymptomatic.

Physical exam

If a person does have symptoms, SLL diagnosis generally starts with a physical exam. During the exam, the doctor will ask the person about any symptoms they are having and review the person’s medical history. The doctor will also check for enlarged lymph nodes and signs of an enlarged spleen in the abdomen.

Blood tests

Based on what the doctor finds during the physical examination, they may then order blood tests. Blood tests that can help a doctor diagnose SLL include:

  • complete blood count (CBC)
  • peripheral blood smear
  • flow cytometry
  • other blood tests

Bone marrow biopsy

While blood tests can determine whether or not a person has SLL, a doctor may still order a bone marrow aspiration and biopsy.

This procedure involves taking a sample of bone marrow from the back of a person’s pelvis. A doctor will then analyze these samples under a microscope. The information from this test can help a doctor determine how advanced or what stage the SLL is.

Learn what to expect during a bone marrow biopsy here.

Additional tests

A doctor may order additional testing to help determine the best course of treatment. These tests can include:

  • genetic tests
  • molecular tests
  • CT scans and other imaging studies

In rare cases, a doctor may order a lymph node biopsy or a spinal tap.

SLL leukemia is a type of non-Hodgkin lymphoma. This cancer is very slow growing. Many people with SLL may not have any symptoms at all.

SLL is very similar to CLL, and the main difference is the part of the immune system the cancer cells affect. There are many treatment options available. The 5-year survival rate for SLL has increased because of medical advances.