What is BCL2?

Reviewed by Pathologists
December 29, 2025

BCL2 is a gene that encodes the BCL2 protein, which helps cells survive.

BCL2 is considered a biomarker. A biomarker is a measurable feature in a tumour, such as a gene change or a protein level, that helps doctors understand how a cancer behaves and how it may respond to treatment. In pathology reports, BCL2 is often mentioned because it plays a vital role in cancers of the blood and lymphatic system.

What is the function of BCL2 in normal cells?

In normal cells, the BCL2 protein helps regulate a process called apoptosis, which is a natural form of programmed cell death. Apoptosis allows the body to remove old, damaged, or unnecessary cells in a controlled way.

BCL2 acts as a pro-survival protein. It prevents cells from dying too easily by blocking signals that would normally trigger apoptosis. This function is especially important in cells that must survive for long periods, such as specific immune cells.

What types of cancer are associated with BCL2?

Abnormal BCL2 activity is most commonly associated with lymphomas, which are cancers of the immune system.

These include:

• Follicular lymphoma.

• Diffuse large B-cell lymphoma.

• High-grade B-cell lymphomas, including so-called “double-hit” and “triple-hit” lymphomas.

• Chronic lymphocytic leukemia.

BCL2 abnormalities can also be seen in other cancers, including some leukemias, multiple myeloma, breast cancer, and certain solid tumours, although the clinical meaning depends on the cancer type.

How does BCL2 cause cancer?

Cancer cells often survive longer than they should. One way this happens is by avoiding apoptosis.

When BCL2 is overactive, it prevents damaged or abnormal cells from dying. This gives cancer cells a survival advantage, allowing them to accumulate and grow over time.

In some lymphomas, BCL2 becomes overactive because of a gene rearrangement, most commonly a change called t(14;18). This rearrangement places the BCL2 gene under the control of powerful growth signals, leading to excessive production of the BCL2 protein.

Other cancers may show increased BCL2 activity through gene amplification, mutations, or changes in gene regulation.

Why do pathologists test for BCL2?

Pathologists test for BCL2 because it can help with diagnosis, classification, prognosis, and treatment selection, especially in lymphomas.

BCL2 testing can help:

• Distinguish follicular lymphoma from benign (noncancerous) lymph node changes.

• Identify aggressive lymphomas that may have a poorer prognosis.

• Supports the diagnosis of certain high-grade lymphomas when combined with other biomarkers such as MYC and BCL6.

• Identify cancers that may respond to drugs that target the BCL2 protein.

Because BCL2 plays a key role in cancer cell survival, it is also an important therapeutic biomarker.

How do pathologists test for BCL2?

BCL2 can be tested using tumour tissue obtained from a biopsy or surgery. Several different laboratory methods may be used, depending on the clinical question.

Common testing methods include:

• Immunohistochemistry, which detects the BCL2 protein inside tumour cells and shows whether it is present at abnormally high levels.

• Fluorescence in situ hybridization (FISH), which looks for rearrangements of the BCL2 gene.

• Molecular tests, such as next-generation sequencing, which can detect mutations or other genetic changes involving BCL2.

In lymphomas, immunohistochemistry is often the first test performed, while FISH or molecular testing may be added for further clarification.

How do BCL2 results appear in a pathology report?

BCL2 results are usually found in sections of the pathology report titled immunohistochemistry, molecular testing, or biomarker studies.

Results may be reported in different ways, including:

• BCL2 positive, meaning the protein is present in tumour cells.

• BCL2 negative, meaning little or no protein is detected.

• BCL2 rearrangement detected, if FISH finds a gene rearrangement.

• No BCL2 rearrangement detected, if testing is negative.

The report may also include comments explaining how the BCL2 result supports a specific diagnosis or whether it has prognostic or treatment significance.

How does BCL2 fit with other lymphoma biomarkers?

BCL2 is usually interpreted together with other lymphoma biomarkers rather than on its own. Examining multiple markers simultaneously helps pathologists determine the exact type of lymphoma and its aggressiveness.

BCL2 is commonly assessed alongside BCL6 and CD10, which are markers of germinal center B cells. When BCL2 is abnormally expressed together with these germinal center markers, it supports a diagnosis of follicular lymphoma rather than a benign (noncancerous) reactive lymph node.

In diffuse large B-cell lymphoma, BCL2 is often evaluated with MYC. When both BCL2 and MYC are strongly expressed, or when both genes show rearrangements, the lymphoma may be classified as a high-grade B-cell lymphoma (sometimes called a “double-hit” or “double-expressor” lymphoma). These lymphomas tend to behave more aggressively and may require different treatment approaches.

BCL2 is also interpreted alongside markers such as CD20, Ki-67, and additional molecular tests to help distinguish between lymphoma subtypes and estimate how quickly the tumour is growing.

By combining BCL2 results with other biomarkers, pathologists can provide a more accurate diagnosis, better risk assessment, and more precise guidance for treatment planning.

Questions to ask your doctor

• Was my tumour tested for BCL2?

• Was BCL2 protein expression or a BCL2 gene change found?

• How do my BCL2 results affect the diagnosis?

• Do my BCL2 results influence prognosis or treatment options?

• Are there other biomarkers that should be tested with BCL2?