Chronic Lymphocytic Leukemia vs. Small Lymphocytic Lymphoma: What’s the Difference?

The two types of blood cancer are more similar than the name implies.

Loading the player...

A blood cancer diagnosis can be complex and confusing. There are four main types of blood cancer: leukemia, lymphoma, and myelodysplastic syndromes, and multiple myeloma. But each of these types can be further broken down into subtypes, such as acute myeloid leukemia or chronic myeloid leukemia. Learn more about types of leukemia here.

One particular pair of blood cancer subtypes stand out, because they share several characteristics, despite falling into two different types of blood cancer (leukemia and lymphoma). These subtypes are called chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL). “[SLL] and CLL are actually the small disease that manifests a little differently,” says Michal Bar-Natan Zommer, MD, assistant professor of hematology and oncology at Mount Sinai Hospital.  

Leukemia is a cancer of the blood and bone marrow. It begins in the early blood cells that form in the bone marrow, according to the Leukemia and Lymphoma Society. On the other hand, lymphoma is a cancer of the lymph system. That includes the lymph nodes, as well as the lymph tissue that’s found in organs around the body (such as the tonsils and spleen).

In people with CLL, the cancer begins in lymphocyte cells, a type of white blood cell, and the “chronic” label refers to the slow progression of the cancer growth. “Chronic lymphocytic leukemia is a very slow-growing leukemia,” says Dr. Zommer. “The majority of the patients are asymptomatic.”

While CLL starts in the bone marrow, it typically spreads. “The cells growing in the [bone marrow and blood] eventually will grow in the lymph nodes, in the spleen, or in the liver,” says Dr. Zommer. Once CLL has spread to the lymph nodes, patients are more likely to experience leukemia symptoms.

Since both CLL and SLL affect lymphocytes and can affect the lymph system, the distinction depends on where the cancer is primarily located. “If the majority of the disease is in the lymph nodes or spleen—with less involvement in the blood and bone marrow—we call it small lymphocytic lymphoma,” says Dr. Zommer. If the cancer is mostly in the blood and bone marrow, it’s CLL.

Treatment for CLL and SLL may begin with the “watch and wait” method. “Some [patients] progress very slowly and the patient will not need treatment for many years,” says Dr. Zommer. If the cancer progresses to a stage that requires treatment, chemotherapy or biological therapies may be used. Learn more about types of treatment for blood cancer here.

“Today the prognosis is better than it was before,” says Dr. Zommer. Lots of ongoing research is providing new ideas, insights, and potential solutions. “Fighting the cancer [has] become easier [and] more successful with time.”