What is Fish Method?

Fluorescence in situ hybridization (FISH) is a test that “maps” the genetic material in a person’s cells. This test can be used to visualize specific genes or portions of genes. FISH testing is done on breast cancer tissue removed during biopsy to see if the cells have extra copies of the HER2 gene. The more copies of the HER2 gene that are present, the more HER2 receptors the cells have. These HER2 receptors receive signals that stimulate the growth of breast cancer cells. The FISH test results will tell you that the cancer is either “positive” or “negative” (a result sometimes reported as “zero”) for HER2.

Figure 1

Where is Fish Method used?

The FISH test is not as common as the Immunohistochemistry test for HER2 detection. However, the FISH test gives more accurate results than the IHC test. Due to the high cost of the FISH test, many laboratories first apply the IHC test. If the IHC test fails to produce a positive or negative result for HER2 in the involved tissue, the FISH test is applied.

Figure 2