Immunohistochemistry

Immunohistochemistry, more commonly referred to as IHC, helps doctors and scientists differentiate between histological subtypes of mesothelioma. IHC does this through the use of antigens, which help to trigger the production of antibodies by the immune system. IHC locates distinct protein antigen markers that are located within mesothelioma tumor cells. By locating these antigens a diagnosis can be made that is more precise than one utilizing imaging scans alone. Mesothelioma can sometimes mimic other illnesses and cancers; IHC is used to differentiate between it and other types of cancer. A more accurate and speedy diagnosis can directly affect a patient’s prognosis.

How IHC Works

Antibodies can also be referred to as immunoglobulins, and are substances that bind with antigens in all living cells. IHC uses this property between the two substances to identify specific cells in a sample. The first step in IHC is a tissue biopsy, which is then sliced into thin sections so that IHC can be conducted on either a slide preparation or a free-floating sample. The tissue sample used for IHC can be either a fresh or frozen sample.
Once a sample has been obtained and prepared a lab technician will introduce specialized antibodies into the specimen usually through the use of a stain or florescent dye. These specimens have been labeled in such a way that they allow identification of the specific antigen proteins associated with the antibodies. Once this reaction has occurred the sample is washed and the markers remain, but only in the tagged cells, making identification possible.

Indirect IHC

Direct IHC is a reaction between the labeled antibody and the antigen. Indirect IHC, however, involves the introduction of two antibodies; a primary unlabeled antibody and a secondary labeled antibody specifically. Indirect IHC is more likely to be used than direct IHC due to its higher level of sensitivity. During indirect IHC cellular events associated with tumors, such as cell death, will become highlighted on the stained tissue sample. These cellular events then help the pathologist or other diagnostician determine the histology of the tumor based on a variety of cellular activity.

Protein Markers

There are two commonly used protein markers for the diagnosis of mesothelioma histological subtypes. Those protein markers are BerEP4 and vimentin. While BerEP4 has yet to be proven in diagnosing mesothelioma directly, it does distinguish between mesothelioma and other forms of cancer. This helps doctors and oncologists to rule out other forms of disease, hopefully expediting the diagnostic process.
Vimentin is a filament protein located within microvilli, which is a useful IHC marker. As is the case with BerEP4, vimentin is useful in differentiating malignant mesothelioma from adenocarcinomas, but it has yet to be proven in distinguishing malignant from benign hyperplastic mesothelial cells reliably.
IHC remains among several methods being researched to help aid medical science as it pertains to early diagnosis of malignant mesothelioma.
References:
Thomas Fisher Scientific
U.S. National Institutes of Health