Monoclonal B-cell lymphocytosis (MBL)

MBL is a pre-cancerous condition, which means it is not cancer, but can increase your risk of developing cancer later on.

MBL may increase your risk of developing a blood cancer called Chronic Lymphocytic Leukemia (CLL). CLL is a cancer of white blood cells called B-cell lymphocytes.  You can learn more about CLL by visiting the CLL information page.

Monoclonal B-cell lymphocytosis (MBL) is a non-cancerous condition that does not need any treatment. However it may increase your risk of developing CLL, so your doctor will want to have regular contact with you to make sure you remain well.

Many people with MBL will never develop CLL however, and you can continue to live a normal life with MBL.

On this page:

Overview of monoclonal B-cell lymphocytosis (MBL)

Monoclonal B-cell lymphocytosis (MBL) is a non-cancerous condition. This condition causes an increased number of abnormal B-cells called lymphocytes in the blood.  Lymphocytes are a type of white blood cell and fight infection.  There are B-lymphocytes (B-cells) and T-lymphocytes (T-cells) that have different roles as part of the body’s immune system.

The abnormal B-lymphocytes have the same characteristics as chronic lymphocytic leukaemia (CLL). MBL is seen as a precursor (pre-cancerous) condition.  CLL is a type of lymphoma that is caused by abnormal B-lymphocytes.  You can learn more about CLL by visiting the CLL information page.

Who does it affect?

The incidence of monoclonal B-cell lymphocytosis (MBL) increases with age. MBL is very rare in people under 40 years of age and only affects around 1% of the population. Around 10% of people affected are over the age of 40 years. Approximately 75% of people affected are over the age of 90 years. 

Risk factors for MBL can include:

  • Family history of chronic lymphocytic leukaemia (CLL)
  • Increasing age
  • Infections that can include hepatitis C, pneumonia, influenza, cellulitis, upper respiratory tract infections and herpes zoster. 

Types of monoclonal B-cell lymphoma (MBL)

There are two types of monoclonal B-cell lymphoma (MBL).  These include low count and high count MBL. 

  • Low count MBL occurs when the number of abnormal lymphocytes in the bloodstream is less than 5000 (<0.5 x 10/9/L). Low count MBL does not progress to the lymphoma, known as CLL. 
  • High count MBL is when the number of abnormal lymphocytes detected in the bloodstream is more than 5000 (>0.5 x 10/9/L). High count MBL has a rare chance (around 1-2%) each year of progressing to CLL. 

If the MBL does progress to become CLL, it is likely that the management will be ongoing monitoring. The majority of people who progress to CLL will live the rest of their natural life span. This is a result of treatments available today and the advances in future treatments.

Diagnosis and staging

If a blood test shows a raised lymphocyte count you will need further investigations. This is to understand the reason why the lymphocyte count is high. It is common to see people with a raised lymphocyte count as a result of infection or because of an autoimmune condition. Generally further investigation is only needed if the lymphocyte count has been high for 3 or more months or if no other medical reason is present.

You will have a blood test and the sample will be sent to a laboratory for testing. A test called flow cytometry can diagnose MBL. Flow cytometry can detect and measure physical and chemical characteristics of a population of cells. 

The biology of the cells present in MBL and CLL is the same. A diagnosis of MBL is dependent on the number of these abnormal lymphocytes. The number of abnormal lymphocytes present in MBL is not high enough to meet the criteria of a diagnosis of CLL. In most cases a blood test is enough to diagnose MBL. People with MBL will have a check-up, usually yearly, to have a blood test and a health assessment.

Some people will need more than a blood test to confirm a diagnosis of MBL and do not have a lymphoma such as CLL;

  • Computed tomography (CT) scan – if there are any concerns around swollen lymph nodes, known as lymphadenopathy
  • Bone marrow biopsy if there are any concerns abnormal cells are in the bone marrow

Waiting for results can be a difficult time.  It may help to talk to your family, friends or a specialist nurse.

Management of monoclonal B-cell (MBL)

People with MBL do not require any treatment.  Patients will attend a specialist appointment yearly. You will usually need a blood test and a clinical examination. It is important to visit your GP (general practitioner or family doctor) on a regular basis. If you are experiencing any worrying symptoms then you should contact your specialist. It may mean that you will need to see your specialist sooner.

Only 1-2% of people with MBL develop CLL. If CLL does develop, around 30% of these people will continue on close monitoring with no treatment ever required.

How to keep healthy living with MBL?

It is important to keep a healthy lifestyle to reduce our risk of getting certain diseases. People with MBL have a higher risk of getting repeated infections and secondary cancers. Below are recommendations for people diagnosed with MBL that include:

  • Protect your skin from sun exposure. When outdoors apply a SPF50+ sunscreen, cover your skin with clothes, wear a hat and sunglasses. 
  • Keep an eye on your skin and report any new or concerning skin spots to your GP. Attend a yearly skin check through your GP or specialist skin cancer clinic
  • Have a blood test to check the level vitamin D. Your GP will tell you if you need to take vitamin D supplements
  • Keep up to date with any immunisations available to you. This includes the yearly influenza vaccine and recommended vaccines when travelling to other parts of the world. Live vaccines are not recommended for people with MBL. An example of a live vaccine is MMR (measles, mumps and rubella. Ensure you check this with your GP
  • Always attend age appropriate cancer screening checks including colonoscopy, mammogram and pap smears

Any further questions contact your specialist or GP. You can also contact one of our nurses on the Lymphoma Nurse Support Line, number as advised below. 

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