What is Colon Cancer IHC testing?
IHC testing looks for four proteins (MLH1, MSH2, MSH6, and PMS2) in your tumor. These proteins help your body’s cells work properly. About 85% of IHC tests are normal, which means that all four proteins are present in the cancer cells. IHC tests are abnormal in about 15% of tests. In these cases, one or more of these proteins are missing from the cancer cells. The majority of colon cancers are caused by chance. However, 5-10% of colon cancers occur because of an inherited cancer risk and tumors missing these proteins account for some of these.
What are the benefits of IHC testing?
Many inherited traits can increase the risk for colon cancer. The most common is a condition called Lynch syndrome. Having Lynch syndrome increases your risk of developing a number of other types of cancers as well. IHC testing cannot confirm a diagnosis of Lynch syndrome, but if you have an abnormal IHC test it means it is possible that you have Lynch syndrome and further genetic testing is recommended. Genetic testing may help diagnose and treat a medical problem. A person found to have an increased risk of disease might choose preventative or therapeutic medical treatments. Knowing about a certain disease gene might also provide important health information for you and your family.
What are the risks of IHC testing?
There is no physical risk of IHC testing because the test is performed on tissue samples that were removed during your colonoscopy. However, the greatest concern that people have is the way IHC testing and other possible genetic testing may change your life. Genetic testing may not give clear answers and it may raise new concerns about your health. A genetic test may reveal unexpected relationships, such as non-paternity (a different biological parent). Genetic tests may also raise concerns with a person’s ability to obtain health, life, disability or long-term care insurance; however there are laws stating that employers and insurance companies cannot discriminate based on genetic information.
Who will have access to the results of my test?
Your test results may be released to your health insurance company, to other health care providers as designated by your provider or other parties covered in the Release of Information (ROI), signed at your first visit. The length of time that a specimen is stored will depend on the facility that processes the sample (typically 2 to 10 years).
How will I receive the results of my test?
Your health care provider will send you your results by mail or discuss the results with you over the phone. Your health care provider may also request that you come in for an office visit to discuss the results of your IHC test.
What do the results of the IHC test mean?
A negative test result means that the laboratory did not find any changes in the proteins of your tumor. This result can indicate that a person is not affected by a particular disorder, is not a carrier of a specific genetic mutation, or does not have an increased risk of developing a certain disease. A negative test does not always rule out the presence of every gene change that could cause a disease. Further testing may be required to confirm a negative result.
A positive test result means that the laboratory found a particular change in the proteins of your tumor. This means that it is possible that you have an inherited genetic condition and further genetic testing is recommended.
In some cases, a test result falls in between the positive and negative range. This type of result is called uninformative, indeterminate, inconclusive, or ambiguous. In such cases, it may not be possible to tell whether a person has a gene change that can cause a disease.