What is immunophenotyping?

Reviewed by Pathologists on:
December 31, 2025

Immunophenotyping is a laboratory method used to identify and classify cells based on the proteins they express on their surface or inside the cell. These proteins act like molecular “name tags” that help pathologists determine what type of cell is present, where it came from, and whether it is normal or abnormal.

Immunophenotyping is most often used to study blood, bone marrow, lymph nodes, and tumour tissue, especially when doctors are evaluating cancers of the immune system or trying to classify a tumour more precisely.

Why is immunophenotyping performed?

Many different cells can look similar under the microscope. Immunophenotyping provides additional information beyond appearance alone, helping pathologists make accurate diagnoses.

Immunophenotyping is commonly used to:

  • Diagnose leukemia and lymphoma.

  • Distinguish between different types of cancer.

  • Determine whether a group of cells is benign (non-cancerous) or malignant (cancerous).

  • Classify tumours more precisely to guide treatment decisions.

How does immunophenotyping work?

Immunophenotyping uses antibodies, which are proteins designed to attach to specific markers on cells. Each antibody recognizes a particular protein. When the antibody binds to its target, it allows the laboratory to detect whether that protein is present.

By testing for multiple proteins simultaneously, pathologists can build a detailed profile of the cell population, known as an immunophenotype.

What tests are used for immunophenotyping?

Immunophenotyping can be performed using different laboratory techniques, depending on the type of sample and the clinical question.

Immunohistochemistry

Immunohistochemistry is performed on tissue samples, such as biopsies or surgical specimens. Antibodies are applied to thin tissue sections on glass slides. Cells that express the target protein become highlighted with a visible stain that pathologists can see under the microscope.

Flow cytometry

Flow cytometry is commonly used on liquid samples, such as blood, bone marrow, or fluid from lymph nodes. Cells are labeled with antibodies and passed through a machine that rapidly analyzes thousands of cells individually. This method is beneficial for diagnosing leukemias and lymphomas.

What kinds of proteins are tested?

The proteins tested during immunophenotyping depend on the suspected diagnosis. Some proteins help identify the cell type, while others help determine how mature or abnormal the cells are.

For example, immunophenotyping may detect markers that indicate:

The specific pattern of proteins helps narrow down the diagnosis.

Why is immunophenotyping important in cancer diagnosis?

In cancer care, immunophenotyping helps pathologists:

  • Confirm the exact type of cancer.

  • Distinguish between cancers that look similar under the microscope.

  • Identify cancers that may respond to specific treatments.

  • Monitor disease over time or assess response to therapy.

Because treatment choices often depend on the exact tumour type, immunophenotyping plays a critical role in personalized care.

Why might immunophenotyping be mentioned in my pathology report?

Your pathology report may mention immunophenotyping if special tests were needed to classify the cells in your sample. The report may list which proteins were tested and whether they were present or absent.

These results help explain how the diagnosis was made and support the final interpretation.

Questions to ask your doctor

  • Why was immunophenotyping performed on my sample?

  • What did the immunophenotyping results show?

  • How did these results help confirm my diagnosis?

  • Do the findings affect my treatment options?

  • Will immunophenotyping be used again to monitor my condition?

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