immunohistochemically

Immunohistochemically is an adverb used to describe findings derived from or detected by immunohistochemistry, a laboratory method that localizes specific antigens within tissue sections using antigen‑specific antibodies. The technique preserves tissue architecture while revealing the spatial distribution of proteins, enabling cellular localization such as nuclear, cytoplasmic, or membranous expression.

The standard workflow begins with tissue preparation, often formalin-fixed and paraffin-embedded (FFPE) or fresh frozen material. Sections are treated to expose epitopes (antigen retrieval), then incubated with a primary antibody targeting the antigen of interest. A secondary antibody conjugated to an enzyme or fluorophore provides visualization, typically chromogenic detection with diaminobenzidine (DAB) or fluorescence. Positive controls confirm antibody performance, while negative controls assess nonspecific staining.

Applications include diagnostic pathology, where immunohistochemical results support tumor classification, determine lineage, or identify prognostic/predictive biomarkers such as ER, PR, HER2 in breast cancer, Ki-67 proliferation index, or p53 status. In research, immunohistochemical techniques map protein expression within tissue context, inform about cellular interactions, and support multiplex analyses.

Interpretation relies on staining pattern, intensity, and distribution, often summarized using semi-quantitative scoring systems. Limitations include variability in fixation, antigen retrieval, antibody specificity, and interpretation. Rigorous controls, standardized protocols, and, when possible, automated staining platforms improve reproducibility. Immunohistochemical results may be complemented by other modalities to corroborate findings.