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What does that mean?

Updated 07.05.2024

Some of the terms and abbreviations used in CLL can be confusing. Here you will find an explanation for the main ones:


A condition where the number of red blood cells is below the normal range. The most common symptoms associated with anaemia include fatigue, weakness and shortage of breath. In extreme cases a blood transfusion may be given.


Antibodies are proteins which help fight infections in your body. Your lymphocytes (white blood cells) produce these naturally but you can also be treated for CLL using antibodies that are created in a laboratory. These are called monoclonal antibodies.

Axilla (axillary)

Refers to the area under the arm (armpit). Often used to describe lymph nodes in this position.

B lymphocyte or B cell

A type of white blood cell normally involved in producing antibodies to fight infection. CLL is a cancer of these cells.


The removal of a small piece of tissue for examination under a microscope.

Blood count, full blood count or FBC

A blood test that counts the different types of cells in your blood.

Bone Marrow

The spongy material inside bones that produces red blood cells, white blood cells and platelets.

Bone marrow biopsy and aspiration

A routine test to see whether or how much cancer is present in the bone marrow. A needle is inserted into the bone marrow, usually in the hip area, to withdraw a sample for analysis.


Treatment using anti-cancer drugs; it can be a single drug or a combination of drugs. Chemotherapy is used to kill cells or stop them growing and dividing. Although it’s aimed at the cancer cells, the treatment also affects normal cells which divide quickly, such as those in the hair and gut. A usual treatment for younger CLL patients is a combination of Fludarabine, Cyclophosphamide and Rituximab (FCR) although there are others that may be used, depending on the patient.

Clinical nurse specialist

A qualified nurse who specialises in a particular clinical area. Some deal with all blood cancers while others may specialise in myeloma, lymphoma or another specific area. Your nurse specialist can provide information and expert advice about your condition and treatment.

Clinical trial

A planned medical research study involving patients. They can be small trials involving only a few patients or large national trials. Clinical trials are always aimed at improving treatments and reducing any side effects they cause. You will never be treated on a clinical trial without detailed explanation of what is involved and your written consent to take part.


The study of the structure of chromosomes. Cytogenetic tests (or FISH tests) are carried out on samples of blood and bone marrow taken from leukaemia patients. They aim to find any changes which could be linked to the disease. They can also help doctors to decide on the treatment you’ll have.


Swelling caused by excessive amounts of body fluid.

Febrile neutropenia/Neutropenia

Neutropenia is when a particular type of white blood cell (the neutrophil) is very low. Neutropenia increases the risk of infection. Febrile neutropenia is when you have neutropenia and a fever. This may indicate that you have an infection and you will need immediate medical review.


Fatigue is a feeling of extreme tiredness which doesn’t go away after rest or sleep. It might be caused by the CLL itself or might be a side effect of treatment. It’s one of the most common problems that people with cancer have.

FISH test

FISH stands for Fluorescent In Situ Hybridisation. This test looks for abnormalities in the cancer cell genes. It is important for determining how the CLL may develop and for choosing what treatment may be necessary. It should always be performed prior to treatment decisions. Often conducted in association with Flow Cytometry (See below).

Flow Cytometry

A procedure that examines the molecular characteristics of cells. This test is key in establishing the exact diagnosis of CLL.

Full Blood Count (FBC)

A routine blood test used to see the number of blood cells (red, white and platelets) in the bloodstream. A FBC is usually done at each appointment with the doctor and enable the progress of your disease to be monitored.


G-CSF is a drug that’s most often prescribed after chemotherapy. It helps increase white blood cells called neutrophils that protect you from infection. Neutrophils are often destroyed during chemotherapy, causing a condition called neutropenia. G-CSF can also increase your number of stem cells before or after a stem cell transplant.


A doctor specialising in blood disorders.


A protein in red blood cells that carries oxygen from the lungs to the body’s tissues and returns carbon dioxide to the lungs.

IgHV test (formally known as IgVH)

A test to see if the immunoglobulin heavy chain (IgVH) gene in the cancer cells is mutated or unmutated. Mutated is more favourable than unmutated, although this distinction is becoming less important with the newer therapies becoming available.


This stands for Intravenous Immunoglobulin and is a blood product used to treat CLL patients who have recurrent, serious infections combined with low levels of immunoglobulin in the blood.

Immune system

The network of cells, tissues and organs which protect your body against infection. See the separate section on the Immune System.


Often referred to as ‘cancer of the blood’, leukaemia is divided into many different types – some which develop faster (acute), and others which develop more slowly (chronic). People with leukaemia have large numbers of abnormal blood cells, usually types of white blood cell, which take over the bone marrow and often spill out into the bloodstream. Other areas that may be affected are lymph nodes, spleen, liver, the membranes surrounding the brain and spinal cord (meninges), gums and skin.

Lymph node or lymph gland

A bean-shaped organ that acts as a filter to catch viruses, bacteria and other foreign materials. It contains white blood cells that fight infection.


A type of white blood cell which is involved in the immune defences of the body.

Lymph vessels

Small tubes which make up a network which runs around your body. They carry a fluid called lymph.

MRD (Minimum Residual Disease)

When a small number of cancer cells remain in the patient during or following treatment (uMRD is undetectable measurable residual disease).


A small genetic change to DNA. These changes are caused by copying mistakes when a cell was dividing. If the mutation affects the way cells normally work, it can lead to a disease.


Neutropenia involves having lower-than-normal levels of neutrophils (a type of white blood cell) in your blood. It’s especially common among people receiving cancer treatments, like chemotherapy. Neutrophils help fight infections. If you have neutropenia, it’s important to take extra precautions to avoid germs that may make you sick. See G-CSF.


A component of blood that is important to prevent bleeding and bruising.

Richter’s Syndrome (RS)

Richter’s Transformation (RT), also called Richter’s Syndrome (RS), occurs when CLL / SLL changes into a related but much more aggressive large cell lymphoma in patients with chronic lymphocytic leukaemia (CLL) or small lymphocytic lymphoma (SLL). 

Often, the transformation is into diffuse large B-cell lymphoma (DLBCL), but other lymphomas are seen, including Hodgkin’s lymphoma which generally has a better prognosis.

As patients with CLL / SLL are living longer, the long-term risk of developing RT is increasing. Most RT is fast moving, unlike CLL / SLL which is usually slow growing or indolent. 


An organ that filters the blood. It sits under your ribs on the left-hand side of your body. The spleen has two main jobs: to remove old red blood cells and to help protect your body from infections. In CLL, the spleen can become enlarged and extend below the rib cage.

Stem cells

Cells that are able to develop into other cell types. Stem cells act as a repair system for your body and replenish other cells. They’re found in embryos and some organs in adults.


The use of radiation in treatment. Radiotherapy kills cancer cells in the area of the body being treated, so it can be an effective treatment for diseases which affect a particular part of the body such as lymphoma and myeloma. It’s very rarely used in CLL.

Refractory disease

A cancer that does not respond to treatment or that relapses soon after treatment.


A lower than normal number of platelets in the blood. Platelets are important in blood clotting and a shortage may result in increased tendency to bleeding or bruising.

Tumour Lysis Syndrome (TLS)

A potential complication during treatment, caused by a drug triggering the quick death of a large number of cancer cells, making them enter the bloodstream, which the kidneys can’t cope with. Some modern treatments are very good at killing cancer cells, so patients are very carefully monitored, and doses of the drug or drugs are gradually increased.

Abbreviations frequently used in CLL

AbbreviationWhat it stands forWhat it means
AIHAAutoimmune Haemolytic AnaemiaOccurs when your immune system makes antibodies that attach to your red blood cells. This causes a drop in the number of red cells.
AEAdverse EffectFor example, if you have a reaction to a drug
ALCAbsolute Lymphocyte CountThis is when the number of cells is expressed as an absolute number, rather than as a percentage. The absolute lymphocytes count can be calculated by multiplying the total number of white blood cells against the percentage of white blood cells which are lymphocytes
BMBone MarrowThe part of the bone that produces blood cells
BMXBone Marrow BiopsyTaking a sample of bone marrow – usually from the hip area – to find out the extent of CLL in the marrow
BRBendamustine and RituximabDrugs used in treatment for CLL. Now being replaced by newer treatments
BTKBruton’s Tyrosine KinaseThis is a critical molecule in the survival of CLL cells. BTK inhibitors, such as Ibrutinib, are designed to block this pathway
CBC or FBCComplete Blood Count or Full Blood CountThe blood test that measures the production of blood cells by the bone marrow. The key elements are: haemoglobin, white blood cells and platelets
CRComplete Response/RemissionThis is the patient’s response to treatment. A CR means that tests show no evidence of CLL
DFSDisease Free SurvivalThe length of time a patient has no detectable disease
DoRDuration of ResponseHow long a treatment keeps CLL at bay
FCRFludarabine, Cyclophamide, RetuximabA chemotherapy treatment for CLL, now being replaced by newer treatments
FISHFluorescence in Situ HybridisationThis is a test that looks at the genetic material in cells, including specific genes or portions of genes. It is used to detect chromosomal abnormalities and other genetic mutations, which may guide treatment choices
HbHaemoglobinA protein found in the red blood cells that carries oxygen around your body and gives blood its red colour. Haemoglobin levels vary from person to person. A low HB = anaemia
IbrIbrutinibAn oral drug used to treat CLL
LDTLymphocyte Doubling TimeThe time taken for the number of lymphocytes in the blood to double. This is used as measure of how your CLL may be progressing
LymphocyteA lymphocyte is a type of white blood cell that is part of the immune system. There are two main types of lymphocytes: B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. CLL cells are derived from B-lymphocytes
LNLymph NodeA lymph node, or lymph gland, is an organ of the lymphoid system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels
PFSProgression Free SurvivalThe amount of time before CLL progresses in a patient
PLTPlateletsPlatelets are part of the blood which help to stop bleeding. They can be low in CLL patients, and this can lead to bruising
PRPartial Response/RemissionThis is when a patient responds to treatment, but not completely
RRituximabA drug used to treat CLL, usually in combination with other drugs
R/RRelapsed/RefractoryThis is when there is a failure to achieve a Complete Remission or a Partial Remission with treatment. Relapsed disease is progression of CLL after achieving either CR or PR for at least 6 months
RBCRed Blood CellRed blood cells contain haemoglobin (Hb) – hence the red colour – and transport Hb around the body
RCHOPRituximab, Cyclophosphamide, Hydroxy daunomycin, OncovinCombination chemotherapy drugs used to treat some CLL patients if they have developed a type of transformation called Richter’s, or to another high-grade lymphoma
RTRichter’s TransformationTransformation of CLL into an aggressive form of high-grade lymphoma
TLSTumour Lysis SyndromeTLS is caused by rapid breakdown of large numbers of cancer cells and subsequent release of the cell content into the bloodstream. This can overwhelm normal bodily functions to remove it. It can be the result of certain treatments and the patient is carefully monitored in case this happens
V + R
(or VenR)
Venetoclax and RituximabTwo drugs used in combination to treat CLL
W & WWatch and WaitAlso called Medical Monitoring. The period of time before treatment when you are checked regularly to see how your CLL may be developing. Studies have shown that treating patients when the diagnosis of CLL is made – even if the patient is well – does not lead to better outcomes than treating patients when the CLL is leading to symptoms, a drop in the level of normal blood cells and/or increasing lymph nodes (in size and in number)