Introduction
Cancer diagnosis by histopathologist involves tissue diagnosis from the tumor.
It is essential to detect the site of origin of the tumor and also the antigens(proteins) they express for which immunohistochemistry is used.
What is a Immunohistochemistry?
[Immuno-antibodies, histo-tissue, diagnosis-to detect]
To detect the specific antigens(proteins) on the tissue certain antibodies are used. These are known as immunohistochemistry. The antibodies are linked to an enzyme/fluorescent dye. After the antibodies bind to the antigen in the tissue sample, the enzyme/dye is activated. This is visualised under the microscope.
A laboratory needs specialised IHC machines and trained technicians and pathologists for carrying out the IHC procedure.
Proper tissue collection, fixation and processing is essential to get appropriate results.
Use of IHC to the Histopathologist
A histopathologist routinely examines the tissue which is stained by Haematoxylin and Eosin which stains different components of tissue like cell membrane, cell cytoplasm, cell nucleus, red blood cells, inflammatory cells with different colours. However, sometimes the tumor cells don’t resemble the cells of the organ of origin. To detect the primary organ from which it originates, it becomes essential to use special stains and IHC.
Utility of IHC-
Immunohistochemistry is used to help diagnose diseases, such as cancer.
It may also be used to help tell the difference between different types of cancer. Eg-Cytokeratins(CK) are used in diagnosis of carcinoma, LCA is used in the diagnosis of lymphoma,TTF1 to diagnose lung cancer.
IHC is an important method for pathologists in routine diagnostic work as well as in basic and clinical research including exploration of biomarkers.
IHC have diagnostic and therapeutic use as there is targeted therapy against some antigens expressed by certain tumours. Eg. As an example, three proteins of particular interest for breast cancer are HER2, the estrogen receptor (ER) and the progesterone receptor (PR).
Helps to differentiate tumors which have the same morphology.
Helps to detect high grade and low-grade tumor. Eg Ki67 labelling index is used.