Diffuse large B cell lymphoma (DLBCL)

by Philip Berardi, MD PhD FRCPC
June 3, 2022


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 B cells. DLBCL is the most common type of lymphoma to affect adults and typically arises in people greater than 65 years old. This type of cancer 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.

Where is diffuse large B cell lymphoma commonly found?

Because B cells are normally found throughout your body, DLBCL can start almost anywhere in your body. B cells are a type of white blood cell that normally plays an important role in protecting you from infections.

What are the 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 is the diagnosis of diffuse large B cell lymphoma made?

The diagnosis of DLBCL is usually made after your doctor removes a small piece of tissue in a procedure called a biopsy. The tissue is then sent to a pathologist for examination under a microscope.

What does diffuse large B cell lymphoma look like under the microscope?

When examined under the microscope, the cancer cells in DLBCL are much larger than normal lymphocytes. The nucleus of the cell also usually contains large clumps of genetic material called nucleoli. Because the cancer cells in DLBCL look very different than normal lymphocytes, pathologists describe it as a high-grade type of lymphoma.

The term pattern of growth describes the way the cancer cells are grouped together when examined under the microscope. DLBCL typically shows a diffuse pattern of growth pattern. This means the tumour cells are spread over a relatively large area. As the tumour grows, it can replace the surrounding normal tissue or organ. If the tumour is large enough it can prevent nearby organs from functioning normally. The damage caused to normal tissue contributes to the symptoms you may be experiencing.

Immunohistochemistry for diffuse large B cell lymphoma

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.

Transformation

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 follicular lymphomasmall lymphocytic lymphoma (SLL), chronic lymphocytic leukemia (CLL), nodal and extranodal marginal zone lymphoma, and lymphoplasmacytic lymphoma.

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.

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