HER-2 is a gene that controls the production of special proteins called HER-2 receptors. About 25% of breast cancers have extra copies of the HER-2 gene, which means that these breast cancers tend to grow very quickly and have a tendency to spread. HER-2 breast cancers respond well to a treatment called Herceptin, which is anti-HER-2 antibody therapy.
There are two tests used to determine whether or not there is too much HER-2:
ICH (ImmunoChemistryHistology) Test, which determines if there is too much HER-2 receptor protein on the breast cancer cell. Results range from 0 (negative), 1+ (negative), 2+ (borderline) to 3+ (positive).
FISH (Fluorescence In Situ Hybridization) Test, which determines if there are extra copies of the HER-2 gene in the breast cancer cells. FISH results are either positive, meaning that the breast cancer cells have extra copies of the HER-2 gene; or negative, indicating that the breast cancer cells have a normal number of copies of the HER-2 gene.
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