HER2 Tumor Marker Test
Reviewed
A test to measure HER2 protein or gene copies in cancer cells to guide treatment decisions. It helps determine if your cancer is HER2 positive (likely to respond to targeted therapy) or HER2 negative (other treatments may be needed).
Preparation and collection
Preparation depends on how your tissue sample will be taken. Ask your health care provider how to prepare. If you are getting medicine to relax or sleep during the procedure, you will probably need to fast for several hours before and have someone take you home.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Blood tests for HER2 are not recommended because it is not clear how blood test results can plan cancer treatment.
- Cancer cells can change over time, so retesting may be needed for recurrent or metastatic disease even if the first tumor was tested.
- IHC score 2+ is borderline (equivocal) and requires additional testing, such as FISH, for a definitive result.
What to do next
Your healthcare provider will interpret your HER2 test results along with other factors to recommend a treatment plan. If your cancer is HER2 positive, targeted therapy may be an option. If HER2 negative, other treatments will be considered. For equivocal results, additional testing is needed.