IHC service used to explore tumour providers to identify the type of cancer a patient has, and its progression. It can also help them determine if cancer has spread (metastasized) and whether the patient has an inherited condition that raises their risk of developing a certain type of cancer.

IHC testing can detect cancer cells by recognizing specific proteins on the cell surface. A pathologist attaches an antibody to the tissue sample that will recognize these specific proteins (antigens). If the antigen is present, the antibody will bind to it. This creates a visible reaction that appears as a color under the microscope. A hematoxylin counterstain is then used to give the slides a blue background, which helps the pathologist view the cells and structures in the tissues.

ELISA Test vs. Western Blot: Key Differences and Applications

Formalin fixation, particularly over extended periods of time, blocks the antigen epitopes on the tissue surface, limiting the utility of IHC staining. A number of methods have been developed to “unmask” the epitopes, including heat-induced epitope retrieval (HIER), although the success of these techniques varies by tissue type and antibody specifications. Vimentin is a commonly used marker to check for loss of epitopes due to long-term fixation.

HIER and other specialized IHC methods can be used to enhance the utility of IHC in tissues that have been fixed and sectioned for H&E analysis. The IHC service is frequently requested for such tissues, and many of the NIEHS’s intramural investigators utilize IHC to investigate novel tumor markers, carcinogenic mechanisms in rodent models, and other basic science questions.