What is EGFR?

Reviewed by Pathologists
December 28, 2025

EGFR stands for epidermal growth factor receptor. It is a gene that provides instructions for making a protein found on the surface of many normal cells. This protein acts as a receptor, meaning it receives signals from outside the cell that tell the cell when to grow and divide.

EGFR is considered a biomarker. A biomarker is a measurable feature in a tumour, such as a gene change or protein abnormality, that helps doctors understand how a cancer behaves and which treatments are most likely to work.

What is the function of EGFR in normal cells?

In healthy cells, the EGFR protein helps control normal cell growth and repair.

When a growth signal binds to the EGFR on the cell surface, the receptor becomes activated and sends a signal inside the cell telling it to grow or divide. Once the signal is complete, the receptor turns off. This careful control helps maintain normal tissue structure and function.

What types of cancer are associated with EGFR?

Changes involving EGFR are most commonly seen in lung cancer, particularly lung adenocarcinoma. EGFR changes can also be found in:

• Some head and neck cancers.

• Certain brain tumours.

• Some cancers of the colon and rectum.

Not all cancers involve EGFR, and the presence of an EGFR change does not determine the stage of the cancer.

How does EGFR cause cancer?

Cancer can develop when growth signals inside a cell are no longer adequately controlled.

In some tumours, the EGFR gene becomes mutated, meaning its DNA instructions have changed. These mutations can cause the EGFR protein to remain constantly active, even when no growth signal is present. As a result, the cell continues to grow and divide without normal regulation, leading to tumour formation.

EGFR mutations are usually acquired, meaning they develop in tumour cells during a person’s lifetime and are not inherited from parents.

Why do pathologists test for EGFR?

EGFR is tested because it is an important predictive biomarker. This means the test result helps predict whether specific treatments are likely to be effective.

In lung cancer, some targeted therapies are designed specifically to block abnormal EGFR signaling. These treatments are most effective when specific EGFR mutations are present. If no EGFR mutation is found, those treatments are unlikely to help, and other options may be considered.

Testing for EGFR allows doctors to tailor treatment to the tumour’s biology.

How do pathologists test for EGFR?

EGFR testing is usually performed on tumour tissue obtained from a biopsy or surgery. In some cases, EGFR can also be tested using a blood sample, often called a liquid biopsy, which looks for tumour DNA circulating in the bloodstream.

Standard testing methods include:

• Polymerase chain reaction (PCR)–based tests, which look for specific EGFR mutations.

• Next-generation sequencing (NGS), which can analyze EGFR along with many other cancer-related genes simultaneously.

• Immunohistochemistry, which may be used in some cancers to measure EGFR protein levels rather than gene mutations.

How do EGFR results appear in a pathology report?

EGFR results are usually found in a section of the pathology report called molecular testing, biomarker testing, or ancillary studies.

Results are commonly reported in one of the following ways:

• EGFR mutation detected, followed by the name of the specific mutation (for example, exon 19 deletion or L858R mutation).

• No EGFR mutation detected, sometimes described as EGFR wild type.

Your report may also include a brief comment explaining whether the result is relevant for targeted therapy. In some cases, the report will state whether the tumour is eligible or ineligible for EGFR-targeted treatment based on the findings.

Questions to ask your doctor

• Was my tumour tested for EGFR?

• Were any EGFR mutations found?

• Is EGFR considered a biomarker in my type of cancer?

• How do my EGFR results affect my treatment options?

• Are there other biomarkers that should be tested?