Burkitt lymphoma

by Rosemarie Tremblay-LeMay MD FRCPC
March 7, 2023

What is Burkitt lymphoma?

Burkitt lymphoma is a type of cancer that starts from specialized immune cells called B cells. It is characterized by a genetic change called a translocation involving the gene MYC. This genetic change allows the cancer cells to divide and create new cancer cells very quickly.

Where in the body is Burkitt lymphoma found?

The parts of the body often involved by Burkitt lymphoma include the bones of the face and the long bones of the arms and legs, the gastrointestinal tract, gonads, kidneys, and breasts. Other sites including the brain and spinal cord may also be involved. Cancer cells can also be found in the blood. This is different from many other types of lymphoma, which often involve small immune organs called lymph nodes.

What type of lymphoma is Burkitt lymphoma?

Doctors divide lymphomas into two groups: Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. Burkitt lymphoma is a type of non-Hodgkin’s lymphoma.

What are the types of Burkitt lymphoma?

There are three clinical subtypes of Burkitt lymphoma, called endemic, sporadic and immunodeficiency-associated. Each subtype is found in a different situation.

• Endemic – This subtype develops in areas where malaria is also found and mostly affects children.
• Sporadic – This subtype is found anywhere in the world and can occur at any age, but most often affects children and young adults.
• Immunodeficiency-associated – This subtype mostly affects people who have also been infected by the human immunodeficiency virus (HIV).

Some cases of Burkitt lymphoma are associated with the Epstein Barr Virus (EBV), most frequently in the endemic variant.

How do pathologists make the diagnosis of Burkitt lymphoma?

The diagnosis of Burkitt lymphoma is usually made after a small piece of tissue is removed in a procedure called a biopsy. The tissue is then sent to your pathologist who examines it under the microscope. Burkitt lymphoma cells divide to create new cancer cells quickly. For this reason, the tumour can be quite large at the time of diagnosis.

What does Burkitt lymphoma look like under the microscope?

When examined under the microscope, the tumour is made up of medium-sized, dark cells, that typically look very similar to each other. Many mitotic figures (tumour cells dividing to create new tumour cells) and lots of apoptotic cells (dying tumour cells) are also seen. A type of immune cell called a macrophage will remove the dying tumour cells. Pathologists call the look of macrophages surrounded by cancer cells “starry sky” because the macrophages are very light in colour while the cancer cells are dark blue.

What other tests are performed to confirm the diagnosis?

Immunohistochemistry

Your pathologist will perform a test called immunohistochemistry to better understand the tumour and to exclude other diseases that can look similar to Burkitt lymphoma under the microscope. Immunohistochemistry is a test that uses antibodies to highlight different types of proteins produced by cells. When the cells produce a protein, pathologists describe the result as positive or reactive. When the cells do not produce the protein, the result is described as negative or non-reactive.

The cancer cells in Burkitt lymphoma come from B-lymphocytes and they produce proteins normally made by B-lymphocytes such as CD20, PAX5 or CD79a. They also produce CD10 and BCL6. The cancer cells produce MYC in almost all cases. Other markers commonly used in the diagnosis of B-cell lymphomas, such as CD5, CD23 or BCL2, are negative.

Pathologists can also use immunohistochemistry to determine how fast the cancer cells are dividing to create new cancer cells. This is called the proliferation index. Ki-67 (also called MIB1) will be positive in cells that are in the process of dividing to produce more cells. The cells of Burkitt lymphoma divide quickly and Ki-67 will be positive in almost all the cells. For this reason, the proliferation index is usually close to 100%.

Molecular tests

Each cell in your body contains a set of instructions that tell the cell how to behave. These instructions are written in a language called DNA and the instructions are stored on 46 chromosomes in each cell. Because the instructions are very long, they are broken up into sections called genes and each gene tells the cell how to produce a piece of the machine called a protein.

Sometimes, a piece of DNA falls off one chromosome and becomes attached to a different chromosome. This is called translocation and it can result in the cell making a new and abnormal protein. If the new protein allows the cell to live longer than other cells or spread to other parts of the body, the cell can become cancer.

Burkitt lymphoma is characterized by a translocation in the gene MYC, which creates a protein by the same name that can be seen by immunohistochemistry. Pathologists usually test for these molecular changes by performing fluorescence in situ hybridization (FISH) on a piece of tissue from the tumour. This type of testing can be done on the biopsy specimen or when your tumour has been surgically removed. This test can be used to help confirm the diagnosis of Burkitt lymphoma.