Why IHC errors are usually technical
Immunohistochemistry (IHC) is indispensable for tumour subtyping, prognostic and predictive markers, but its reliability rests almost entirely on the pre-analytical phase. Cold ischaemia time, fixative type and duration, and antigen retrieval determine whether an epitope survives to be detected.
Common false positives
- Edge and crush artefact mistaken for membranous positivity.
- Endogenous biotin or pigment misread as signal.
- Non-specific trapping in necrotic or oedematous areas.
Common false negatives
- Under-fixation or excessive fixation altering epitopes.
- Prolonged ischaemia degrading labile antigens (e.g. phospho-epitopes, ER/PR).
- Suboptimal antigen retrieval or over-digestion.
Controls are non-negotiable
A positive control validates the run; an appropriate negative control flags background. Interpreting any marker without seeing its controls is a frequent source of error. Tissue with internal controls (e.g. normal epithelium) adds confidence.
The lab-quality link
Consistent fixation and processing protect epitope integrity before IHC ever begins. Standardised tissue processing and reproducible staining reduce batch variability and the need to repeat marker panels.