What does immunohistochemistry mean? Immunohistochemistry is a commonly used test. Immunohistochemistry is based on the targeted one-to-one combination of antigen and antibody, with the antibodies labeled in vitro with special fluorescence in advance, and a positive result can be seen on the histochemical test if there is a paired antigen when the labeled antibody is stained with the taken tissue section. Immunohistochemical tests are more accurate in their localization, more sensitive in their detection, and can analyze specific molecules in the tissues taken, so they are very useful for diagnosis, prognosis, and determining the type of pathology.