mmunohistochemistry is routinely employed to identify Prognostic Biomarkers, providing crucial information on the likely long-term outcome and aggressiveness of a patient's disease, separate from the tumor's stage. Key prognostic indicators include the proliferation marker Ki-67, which measures the growth fraction of a tumor; high expression often correlates with faster growth and a more aggressive clinical course in cancers like breast cancer.

Furthermore, IHC is essential for identifying predictive biomarkers that determine eligibility for targeted therapies. The detection of hormone receptors (ER/PR) in breast and prostate cancers guides endocrine therapy decisions. More recently, the identification and scoring of programmed death-ligand 1 (PD-L1) expression on tumor and immune cells are mandatory for determining which patients will benefit from immune checkpoint inhibitors. The reliability and cost-effectiveness of IHC make it the standard frontline test for these critical therapeutic decisions in oncology.