Immunohistochemistry

Function

Immunohistochemistry (IHC) is a laboratory technique used to visualize the distribution and localization of specific proteins (antigens) within a tissue section. By using antibodies that bind specifically to these proteins, and tagging those antibodies with a visible color or fluorescent dye, pathologists can see exactly which cells are expressing which markers under a microscope.

Why it is Ordered

IHC is the gold standard for characterizing tumors. When a biopsy is taken, a standard stain (H&E) shows what the cells look like, but IHC tells the pathologist what the cells are. It is used to determine if a cancer is a carcinoma, sarcoma, or lymphoma, and to identify the primary site of a cancer that has spread (metastasis). It is also used to test for specific 'targets' like HER2 in breast cancer to see if certain drugs will work.

Associated Conditions

• Cancer Subtyping: Distinguishing between different types of lung or breast cancer.
• Predictive Markers: Checking for ER/PR (Estrogen/Progesterone) receptors in breast tissue.
• Infectious Disease: Detecting viral proteins (like CMV or HPV) directly within tissue cells.
• Lynch Syndrome Screening: Testing for DNA mismatch repair (MMR) proteins in colon cancer specimens.