Words to know: Chronic lymphocytic leukemia (CLL)
- Lymphocyte
- A type of white blood cell that helps fight infection. CLL starts in B lymphocytes (B cells).
- B cell
- A lymphocyte that makes antibodies. CLL is a cancer of B cells.
- Bone marrow
- The soft tissue inside bones where blood cells are made.
- Small lymphocytic lymphoma (SLL)
- The same disease as CLL, but found mostly in the lymph nodes instead of the blood.
- Monoclonal B-cell lymphocytosis (MBL)
- A small number of CLL-like cells in the blood, below the level of CLL. It is not cancer and is watched with blood tests.
- Flow cytometry
- A lab test that reads markers on cells to show whether they are CLL cells.
- Watch and wait
- Careful checkups and blood tests without treatment, used for early CLL. Also called active monitoring.
- Rai and Binet stages
- Two systems that stage CLL using a blood count and physical exam.
- FISH
- A lab test that looks for missing or extra pieces of chromosomes in CLL cells.
- del(17p)
- A missing piece of chromosome 17. It is a high-risk feature that means chemotherapy works poorly.
- TP53
- A gene that helps control cell growth. Changes in it are a high-risk feature in CLL.
- IGHV
- A gene in B cells. Whether it is mutated or unmutated helps predict how CLL will act.
- BTK inhibitor
- A pill, such as acalabrutinib, zanubrutinib, or ibrutinib, that blocks a protein CLL cells need to grow.
- Venetoclax
- A pill that blocks BCL2, a protein that helps CLL cells stay alive.
- Obinutuzumab
- An antibody given by IV that attaches to CD20 on CLL cells and helps the immune system destroy them.
- Fixed-duration treatment
- Treatment given for a set time, such as 1 year, and then stopped.
- Continuous treatment
- Treatment taken every day for as long as it works and side effects are okay.
- Tumor lysis syndrome (TLS)
- A problem when many cancer cells die at once and release salts that can harm the kidneys and heart.
- MRD (measurable residual disease)
- Tiny amounts of CLL left after treatment, found only with very sensitive tests.
- Hypogammaglobulinemia
- Low levels of antibodies in the blood, which raises the risk of infection.
- IVIG
- Intravenous immunoglobulin. An infusion of antibodies from donors to help prevent infections.
- Atrial fibrillation
- An irregular, often fast heartbeat. It can be a side effect of BTK inhibitors.
- Autoimmune hemolytic anemia
- When the immune system destroys red blood cells. It can happen with CLL.
- Richter transformation
- A rare change of CLL into a fast-growing lymphoma.
- CAR-T cell therapy
- A treatment where your own T cells are changed in a lab to attack cancer, then given back to you.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.