Immunohistochemistry - HER 2

 HER 2 or c-erbB-2, is one of the most widely used antibodies in Immunohistochemistry. This antibody is one of the most commonly tested antibodies as its expression in breast carcinoma can help determine treatement of the patient.

Picture 1 – HER2 in use

This antibody is mainly used to assist in determination of whether a breast case will respond to herceptin by working out the whether it is a HER2+ tumour. This stains up the membrane of breast epithelial cells with around 30% of these cases positive with HER2. However HER2 can also be useful for diagnosis of other carcinoma cases including those from the gastrointestinal tract as well as osteosarcoma and also bladder carinoma.

HER2 positivity requires validation by use of several different levels of positivity to determine the level of Herceptin receptor.

Picture 2 – HER2 ranging 1+ to 3+ positivity

As you can see above, the level of positivity can vary and this is very important in the determination of whether the patient can be treated. Normally a 3+ positivity is required for treatment of a patient using herceptin. However patients with a 2+ or borderline will normally be tested using FISH or fluorescent insitu hybridisation to determine whether the patient can be treated.