What is primary mediastinal large B-cell lymphoma?

Primary mediastinal large B-cell lymphoma (PMBCL) is a type of non-Hodgkin lymphoma (NHL). It is sometimes called primary thymic mediastinal lymphoma.

PMBCL develops when B-cells become abnormal (cancerous). B-cells are white blood cells that normally help fight infection. They are sometimes called B-lymphocytes.

The abnormal B-cells (lymphoma cells) usually develop in a part of the lymphatic system called the thymus gland. They then build up in lymph nodes behind the breastbone and between the lungs. This area is called the mediastinum. It contains:

  • the gullet
  • the windpipe
  • the thymus
  • the heart
  • some large blood vessels
  • some lymph nodes.

Symptoms of primary mediastinal large B-cell lymphoma

Symptoms of primary mediastinal large B-cell lymphoma (PMBCL) may be caused by the lymphoma pressing on structures in the chest. This can cause:

  • a cough
  • aching in the chest
  • breathlessness
  • a hoarse voice
  • swelling in the neck, arm or face
  • dizziness
  • headaches that are worse when bending forward.

Some of these symptoms can be caused by lymphoma pressing on a large vein in the chest. This vein is called the superior vena cava (SVC). It carries all the blood from the upper half of the body to the heart. Pressure on the SVC can block blood from flowing along it. Doctors call this superior vena cava obstruction (SVCO).

B symptoms

Some people also have symptoms that doctors call B symptoms. These can include:

  • drenching night sweats which require a change of nightwear and bed covers
  • high temperatures (fevers) with no obvious cause
  • unexplained weight loss.

Knowing if you have any B symptoms will help your doctor to stage the lymphoma and plan your treatment.

Causes of primary mediastinal large B-cell lymphoma

The causes of primary mediastinal large B-cell lymphoma (PMBCL) are not known.

Like other cancers, PMBCL is not infectious. It cannot be passed on to other people.

We have more information about causes and risk factors for non-Hodgkin lymphoma (NHL).

Diagnosis of primary mediastinal large B-cell lymphoma

Biopsy for lymphoma

The most common test for diagnosing lymphoma is a biopsy. A doctor will take a sample of tissue from the affected area. The most common place to take a biopsy from is an enlarged lymph node. This is called a lymph node biopsy). You may have all or a part of the lymph node removed. The tissue will be sent to a laboratory for testing. You may also have biopsies taken from other areas of your body.

You can read more about further tests you may have in our information about non-Hodgkin lymphoma.

Waiting for test results can be a difficult. You may find it helpful to talk to your family, friends or specialist nurse.

The stages and grades of primary mediastinal large B-cell lymphoma

Your test results will help your doctors find out how many areas of your body are affected by lymphoma and where these areas are. This is called staging. Doctors may use the term bulky disease to describe tumours in the chest that are 10cm (4 inches) across or bigger.

Lymphomas are also grouped as either low-grade or high-grade. Low-grade lymphomas are usually slow growing. High-grade lymphomas usually grow more quickly. Primary mediastinal large B-cell lymphoma (PMBCL) is a high-grade lymphoma.

Knowing the stage and grade of the lymphoma helps your doctor plan the right treatment for you.

We have more information about the stages and grades of non-Hodgkin lymphoma.

Treatment for primary mediastinal large B-cell lymphoma

A team of specialists will meet to discuss the best possible treatment for you. They are called a multidisciplinary team (MDT).

Your doctor, or cancer specialist or nurse will explain the different treatments and their side effects to you. They will also talk to you about things to consider when making treatment decisions.

Primary mediastinal large B-cell lymphoma (PMBCL) is fast-growing and needs to be treated quickly. The aim of treatment is to get rid of all signs of the lymphoma and to cure you.

Some treatments for PMBCL can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor, cancer specialist or nurse before you start treatment.

Treatment for PMBCL depends on the stage of the lymphoma and whether you have symptoms that are causing problems.

The most common treatments for PMBCL are:

  • Immunotherapy and chemotherapy

    PMBCL is often treated with a combination of the immunotherapy drug rituximab and chemotherapy. This is called chemoimmunotherapy. Commonly used combinations of chemoimmunotherapy for PMBCL include:


  • Steroids

    Steroids are drugs that are often given with chemotherapy to treat lymphomas. They help make chemotherapy more effective.

  • Radiotherapy

    Radiotherapy uses high-energy rays to destroy cancer cells, while doing as little harm as possible to normal cells. Some people have radiotherapy after chemotherapy and rituximab to treat an area of lymphoma. It can also reduce the risk of lymphoma coming back in that area.

  • Stem cell transplants

    Stem cell transplants are sometimes used to treat lymphoma that has come back after treatment. Stem cell transplants are intensive treatments, so they are not suitable for everyone. You may have a transplant using your own stem cells autologous stem cell transplant or cells from a donor allogeneic stem cell transplant.

  • CAR-T cell therapy

    CAR-T cell therapy is sometimes used to treat PMBCL that has come back after treatment. CAR-T therapy (chimeric antigen receptor therapy) involves collecting your own immune cells and reprogramming them. The cells are then used as a treatment to target the lymphoma cells. CAR-T therapy can be used when the lymphoma is advanced and when other treatments have failed. CAR-T therapy is complicated and can have serious side effects. It is only available in a few specialist hospitals.

You may have some treatments as part of a clinical trial.

PMBCL usually responds well to treatment. But if it does not respond or if the lymphoma comes back, you will need more treatment.

We have more information about treating lymphoma that has come back.

After treatment for primary mediastinal large B-cell lymphoma

You will have regular follow-up appointments after your treatment. You can talk to your doctor or nurse about any concerns you may have at these appointments. Your doctor will want to know how you are feeling, and to check you are recovering from any side effects of treatment.

Late effects

Sometimes side effects may continue or develop months or years after treatment. These are called late effects. We have more information about long-term and late effects of treatment for lymphoma.

Sex life and fertility

Cancer and its treatment can sometimes affect your sex life. There are ways to improve your sexual well-being and to manage any problems.

Treatment for lymphoma may affect your fertility. If you are worried about your fertility it is important to talk with your doctor before you start treatment. We have more information about:

Well-being and recovery

Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.

Making small changes such as eating well and keeping active can improve your health and wellbeing and help your body recover.

Getting support

Everyone has their own way of dealing with illness and the different emotions they experience. You may find it helpful to talk things over with family and friends or your doctor or nurse.

Macmillan is also here to support you. If you would like to talk, you can:

The organisations below also offer information and support:

  • Blood Cancer UK

    Blood Cancer UK offers support and information to people affected by blood cancers, including lymphoma.

  • Lymphoma Action

    Lymphoma Action gives emotional support, advice and information for people with Hodgkin lymphoma or non-Hodgkin lymphoma and those close to them. It has a national network of people with lymphoma, as well as local groups. Their website has a section called trialslink where you can see information about lymphoma clinical trials.

About our information

  • References

    Below is a sample of the sources used in our primary mediastinal large B-cell lymphoma (PMBCL) information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Vitolo U, Seymour JF, et al. Extranodal diffuse large B-cell lymphoma and primary mediastinal B-cell lymphoma: ESMO Clinical Practice Guidelines. Annals of Oncology. 2016. 27 (Supplement 5), v91-v102. Available from: www.annalsofoncology.org/article/S0923-7534(19)31640-0/pdf

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Professor Rajnish Gupta, Macmillan Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Reviewed: 31 January 2021
Reviewed: 31/01/2021
Next review: 31 January 2024
Next review: 31/01/2024