Flow cytometry testing is one way your lymphoma care team may diagnose and monitor your condition. Doctors use flow cytometry to make sure you’re on the correct treatment course to lead to remission — which occurs when your cancer signs are reduced or disappear completely.

This article will discuss what flow cytometry is, how it relates to lymphoma, and the ways it can be useful. Understanding flow cytometry testing can help you feel more comfortable with upcoming appointments and when reading your lab results.

What Is Flow Cytometry?

Flow cytometry is a lab test (also known as an assay) that finds cancer cells within a blood or tissue biopsy sample. This test works by using fluorescence, or special lights, to see immunological markers on the surface of cells. By studying these markers, doctors can tell whether cells are lymphoma cells.

How Does Flow Cytometry Work?

With flow cytometry testing, a doctor will take a biopsy (a small sample) of the area they think may contain cancer cells. Typically, if your doctor suspects lymphoma, they will order a sample from a lymph node. A lymph node is a small, bean-sized gland that is part of your lymphatic system, a network of vessels and lymphoid tissue that helps your body fight infections. Your doctor could also order a bone marrow biopsy, blood sample, or another tissue sample. This sample may be obtained through a core biopsy or fine-needle aspiration.

Once the pathologist or lab technician has your sample, they will mark your cells with fluorescent dye that allows the cytometer machine to determine which markers each of your cells have.

In flow cytometry, the cells flow single file through a network of tubes while the machine shines lights through the cells to look at the properties (or morphology) of each cell. The process of examining cells is called cytology.

Flow cytometry uses light from lasers that cause the marked cells to fluoresce (emit light). This helps determine which type of cell is present and which cell markers are lit up by the fluorescent dyes. This technology can also look at a cell’s DNA and even see if the cell is actively dividing or not.

Pathologists use a strategy called gating to visualize and map flow cytometry results. Gating refers to a computer analysis for identifying cell populations by the number of each type of cell and their unique cell markers. This helps determine which lymphoma subtypes are present.

The process of tracking which cells are present is called phenotyping. With B- and T-cell lymphomas, this process is specifically looking for differences in these B and T immune cells. Therefore, this type of phenotyping is also known as immunophenotyping or flow cytometric immunophenotyping. From this information, doctors can understand which cells are there, whether they are cancerous, and whether they might respond to certain treatments.

When Is Flow Cytometry Used?

Flow cytometry can be used to diagnose and monitor leukemia and lymphoma. Typically, flow cytometry tests are ordered as a follow-up to a complete blood count test or a white blood cell differential test. This is especially important if those blood tests showed abnormal cells.

Flow cytometry is also used to monitor minimal residual disease (MRD). “MRD” refers to the number of cancer cells that remain in the body after cancer treatment. Tracking MRD helps measure your response to treatment, telling your doctor how well the initial treatment for lymphoma is working. If a standard treatment regimen is not working well enough, your doctor may recommend making changes to treatment that will be more effective in obtaining remission.

Monitoring MRD can help your doctor predict in advance when a relapse may be about to happen and start treatment sooner to keep you in remission. MRD measurement can also help your doctor predict which treatment for relapse might benefit you most.

What Does Flow Cytometry Testing Tell Your Doctor?

Flow cytometry testing is essentially a “cell-sorting station.” It can tell your doctor many things about your cells, including:

• The number of cells
• The shape of your cells
• The types of cells that are present
• The specific cell markers your cells have

There are more than 90 subtypes of non-Hodgkin lymphoma and five subtypes of Hodgkin lymphoma. Flow cytometry can be used to diagnose and monitor these different types of lymphoma, including:

• Chronic lymphocytic leukemia/small lymphocytic lymphoma
• Burkitt lymphoma
• Diffuse large B-cell lymphoma
• Follicular lymphoma
• Anaplastic large cell lymphoma
• Peripheral T-cell lymphoma
• Cutaneous T-cell lymphoma

Some B-cell lymphomas cause your plasma cells (or antibody-producing cells) to make a subset of abnormal antibodies. These antibodies can also be monitored in your blood to track disease progression.

Antibodies are made of different proteins called kappa light chains and lambda light chains. Your plasma cells can also release free kappa light chains and lambda light chains into your blood. When the ratio of kappa to lambda light chains in your blood is abnormal, it can indicate certain types of lymphomas. This kappa-to-lambda light chain ratio can be determined by flow cytometry testing.

How Do Flow Cytometry Results Shape Your Treatment Plan?

Flow cytometry results can shape your treatment plan at different stages. Flow cytometry can be used to diagnose lymphoma, to determine when it’s time to start treatment, to see whether the treatment is effective, and to monitor for signs of relapse during and after treatment.

During Lymphoma Diagnosis

Flow cytometry testing can be used to identify the presence of lymphoma and determine which subtype of lymphoma may be present. With this information, your doctor may choose the best treatment plan for your specific case.

Flow cytometry can also determine the number of lymphoma cells that are present, which can help your doctor decide how aggressive the treatment should be. Some results may indicate that you do not need to begin treatment yet and instead should enter a period of “watchful waiting.”

During Watchful Waiting

Depending on the type of lymphoma, your doctor may recommend a period of active surveillance, also called watchful waiting. Some types of lymphoma are slow-growing and may not require immediate treatment. Flow cytometry can be used during this waiting period to monitor growth and progression, so your doctor will know when it’s the right time to start treatment.

During Treatment

Once you begin treatment, flow cytometry can be used to determine how effective your treatment is. There are a variety of treatment types, including:

• Chemotherapy
• Radiation therapy,
• Bone marrow transplants
• Specialized treatments such as chimeric antigen receptor (CAR) T-cell therapy

Depending on your diagnosis, your doctor will help you choose a treatment strategy that is right for you. Flow cytometry can be used to inform your doctor about whether the chosen treatment is working and whether any adjustments are needed.

After Treatment

Your doctor may recommend occasional flow cytometry tests to monitor your lymphoma after treatment. Flow cytometry can confirm there are no lymphoma cells present or that lymphoma cells aren’t continuing to grow and divide. Proliferation in lymphoma cells can indicate a relapse. Flow cytometry can reveal early signs that you may have a risk of relapse and can help monitor your lymphoma once you are in remission.

Talk With Others Who Understand

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