Diffuse large B-cell lymphoma (DLBCL)

What is diffuse large B-cell lymphoma?

Diffuse large B-cell lymphoma (DLBCL) is a type of cancer that starts from specialized immune cells called lymphocytes. Because lymphocytes are normally found throughout your body, DLBCL can start almost anywhere in your body. Lymphocytes are a type of white blood cell that normally plays an important role in protecting you from infections.

Diffuse large B-cell lymphoma is the most common type of lymphoma to affect adults. It is a disease that can affect people of any age but is more common in older adults (greater than 65 years old). This disease is slightly more common in men.

DLBCL is an aggressive tumour which means the cancer cells can grow and spread quickly to other lymph nodes and organs in your body. For this reason, your doctor will probably recommend starting treatment right away.

The immune system

Your immune system is made up of many different kinds of cells and each plays an important role in protecting your body from infections and helping you heal after an injury. Unlike other types of organs, your immune system is spread throughout your body. Most immune cells are found in small organs called lymph nodes. Lymph nodes are located throughout your body. Large numbers of immune cells can also be found in the blood, skin, gastrointestinal tract, and bones.

Symptoms of diffuse large B-cell lymphoma

The symptoms of DLBCL include a new lump or mass somewhere in the body, weight loss, fatigue, or unexplained sweating during the night.

How do pathologists make this diagnosis?

The diagnosis of DLBCL is usually made after your doctor removes a small piece of tissue in a procedure called a biopsy. Additional tests including immunohistochemistry and flow cytometry may also be performed.

Immunohistochemistry is a test that allows pathologists to learn more about the types of proteins made by specific cells. Cells that produce a protein are called positive or reactive. Cells that do not produce a protein are called negative or non-reactive.

Immunohistochemistry is routinely performed on tumours that look like DLBCL to confirm the diagnosis and to exclude other diseases that have a similar look under the microscope.

Diffuse large B-cell lymphoma typically shows the following immunohistochemistry results:

  • CD20 – Positive.
  • PAX5 – Positive.
  • BCL2 – Positive (Occasionally negative).
  • BCL6 – Positive.
  • CD10 – Positive or negative.
  • MUM1 – Positive or negative.
  • CD23 – Negative.
  • CD3 – Negative.
  • CD5 – Negative.
  • Cyclin D1 – Negative.

Tumours that are positive for CD10 are called germinal center B-cell (GCB) type. In contrast, tumours that are negative for CD10 and positive for MUM1 are called non-germinal center B-cell (non-GCB) type.


Grade is a word pathologists use to describe how different the cancer cells look compared to normal lymphocytes. When examined under the microscope, the cancer cells in DLBCL are much larger than normal lymphocytes. They also usually have large nucleoli. For these reasons, DLBCL is considered a high-grade lymphoma.

Transformation from a low-grade lymphoma

Other less aggressive or low-grade types of lymphoma can change over time into DLBCL.  Pathologists call this type of change a transformation.

Low-grade lymphomas that can turn into DLBCL include:

Exactly how and why this change occurs is still not entirely understood, but it is thought to be related to many different factors. Some of these factors include gene mutations in the cancer cells themselves. Others believe that there are changes to our immune system that allow lymphoma cells to grow more quickly and transform into high-grade disease.

Whatever the cause, a low-grade lymphoma that transforms into a high-grade lymphoma behaves more aggressively. There are usually some different treatment options to consider at the time of lymphoma transformation. These can be discussed with your doctor. The goal is to make sure that your treatment plan suits your personal situation. This means that your treatment plan may be slightly different than someone else you know with the same disease.

Pattern of growth

The pattern of growth describes the way the cancer cells are grouped together when examined under the microscope. Diffuse large B-cell lymphoma typically forms a diffuse growth pattern of medium to large size cells. This means the large abnormal cells are spread over a relatively large area. As the tumour grows, it can replace the surrounding normal tissue or organ. The damage caused to normal tissue contributes to the symptoms you may be experiencing.

Unlike the less aggressive or low-grade lymphomas, DLBCL is usually more invasive which means the cancer cells can grow beyond the tissue where the tumour started and into neighboring tissues or organs. If the tumour is large enough it can prevent nearby organs from functioning normally.

by Philip Berardi, MD PhD FRCPC (updated July 2, 2021)
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