Breast Cancer Fluorescence In Situ Hybridization (FISH) on Tumor Specimen

FISH testing, or fluorescence in situ hybridization, is a laboratory test that looks at breast cancer cells for specific genetic changes, such as extra copies of the HER2 gene. Knowing whether these changes are present helps your care team understand how your cancer behaves and choose the treatments most likely to work for you.

Breast Cancer FISH (Fluorescence In Situ Hybridization) is a specialized lab test used to examine the genetic makeup of cancer cells in a breast tissue sample. It uses fluorescent probes to identify specific genetic abnormalities, such as extra copies of certain genes or chromosomes, which can influence how cancer behaves and responds to treatment.

Your doctor may recommend this test to find out whether your breast cancer cells have too many copies of the HER2 gene or make too much of the HER2 protein. This information matters because targeted therapies work differently from chemotherapy, and knowing your HER2 status helps guide the most effective treatment plan for your situation.

Your healthcare provider may recommend Breast Cancer FISH testing if you have breast cancer and need to assess genetic markers that could impact treatment choices, such as targeted therapies or the need for additional testing (e.g., HER2 status). It’s often used alongside other tests like immunohistochemistry (IHC) or molecular assays.

The sample for FISH testing usually comes from tissue that was already removed during a biopsy or surgery to take out the tumor, so in most cases no additional procedure is needed. A pathologist prepares thin sections of the tissue, places them on glass slides, and applies special dyes so the cells can be examined under a fluorescent microscope.

A small sample of your breast tissue is taken during surgery or a biopsy. The sample is then processed in the lab and prepared for FISH analysis, where fluorescent dyes highlight specific genetic regions under a microscope.

A positive result means the cancer cells have extra copies of the HER2 gene, which is called HER2 positive, and targeted drugs that block HER2 may be an option for you. A negative result means no extra copies were found, so your care team will consider other treatment approaches. Your doctor will explain exactly what your result means for your care plan.

Results show whether certain genetic markers (e.g., gene amplifications, deletions, or rearrangements) are present in your cancer cells. These findings help determine the most appropriate treatment path, including whether you may benefit from targeted drugs or further genetic testing.