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FDA-approved kits use one of three methods to quantify Her-2/neu overexpression in breast tumors. The first is immunohistochemistry (IHC), which involves a semiquantitative, microscopic assessment of antibody reactivity on a fixed tissue sample. Studies have shown that when specimens are carefully handled, IHC results correlate well with Her-2/neu copy number. The test uses a conventional microscope, can be automated, and has a relatively low cost. Some challenges of IHC include consistent tissue preparation and control assays. Commercially available and FDA-approved IHC kits include the InSite Her-2/neu kit (BioGenex), available in both manual and automated forms. The automated form is compatible with the BioGenex i6000 system. Other tests, which can also be automated, are the HercepTest (Dako Corporation) and PATHWAY (Ventana Medical Systems). The Ventana PATHWAY offers an integrated system of IHC plus a reflex FISH assay (see below).
Fluorescent in situ hybridization (FISH) involves the hybridization of specific DNA probes, which are visible on a fluorescent microscope. FISH is compatible with all kinds of tissue, whether fixed or not. Like IHC, FISH is also amenable to automation. A particular benefit of FISH is that it contains an internal control: a chromosome 17 probe not asso
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