In situ hybridization methods are used to identify specific nucleic acid target sequences (DNA or RNA) in a tissue sample. Two main types of in situ methods are used in histopathology are:
- Chromogenic (CISH)
- Fluorescent (FISH)
Chromogenic in situ hybridization (CISH) can identify genetic anomalies that provide diagnostic and prognostic information within the tissue, cells, and/or nucleus. Fluorescent methods also identify specific genetic anomalies and differ from CISH, predominately in the use of fluorescent tags for specific loci.
In situ methods provide a high information content and are used to validate equivocal IHC results. The primary protocol steps in these methods include:
- Sample preparation
- Target hybridization
- Single amplification and detection