Inform HER2 Dual ISH is a test used to figure out if breast cancer cells are HER2-positive. ISH stands for "in situ hybridization."
The Inform HER2 Dual ISH test was approved by the U.S. Food and Drug Administration in June 2011.
HER2-positive breast cancers make too much of the HER2 protein, which receives signals telling the breast cancer to grow. About one out of every four breast cancers is HER2-positive. Figuring out the HER2 status of a breast cancer is an important step in deciding on a treatment plan. The targeted therapy medicines Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib) are used to treat HER2-positive breast cancers.
The Inform HER2 Dual ISH test uses a special stain that makes HER2 proteins change color. After the stain is applied to the breast cancer tissue sample, the sample is examined with a regular microscope.
The Inform HER2 Dual ISH test can be used on tissue samples that have been stored in wax or other chemicals. With the Inform HER2 Dual ISH test, you get a score of either "HER2-positive" or "HER2-negative."
Research has shown that some HER2 status test results may be wrong. This is probably because different labs have different rules for classifying positive and negative HER2 status. Each pathologist also may use slightly different criteria to decide whether the results are positive or negative. In most cases, this happens when the test results are borderline -- meaning they aren't strongly HER2-positive or HER2-negative.
In other cases, tissue from one area of a breast cancer can test HER2-positive and tissue from a different area of the cancer can test HER2-negative.
The Inform HER2 Dual ISH test offers more precise results than the IHC HER2 test. It also is less expensive and doesn't need the special microscope of the FISH HER2 test.
If your HER2 test results are negative or borderline, it's a good idea to ask your doctor which type of test was done. If only an IHC test was done, a reading of 0 or 1+ is considered negative. A 3+ result is considered positive. If your IHC result is 2+ (which is considered borderline), ask if you can have a more precise test, such as the Inform HER2 Dual ISH test, the SPoT-Light HER2 CISH test, or the FISH test.