Insitu Hybridisation including FISH

This technique has been regarded as a research tool but improved technologies (proprietary kits and integrated instruments for automated immunohistochemistry and in-situ hybridisation) are leading to clinical applications. In-situ hybridisation may be used to detect viral nucleic acid, examples being the detection of EBV in post-transplant lymphoproliferative disorders or HPV subtyping in cervical biopsies. In-situ hybridisation for k and \ light chain mRNA may have advantages over conventional immunohistochemistry. Fluorescence in-situ hybridisation (FISH) may be used to detect karyotypic abnormalities in the intact interphase nucleus such as HER2/neu amplification in breast cancer, particularly in patients with equivocal immunohistochemistry, and n-myc amplification in neuroblastoma. It can also be used to detect translocations but this is technically very difficult and has not been adopted widely. The development of antibodies detecting fusion gene proteins (e.g., NPM-ALK) and the availability of PCR and rt PCR (reverse transcriptase polymerase chain reaction) based methods for translocation detection may prevent the further development of such assays. FISH requires access to a good fluorescence microscope with appropriate filter sets and a low-light CCDTV camera to capture and digitise images. It is a specialised technique only available in a small number of large centres. Routinely fixed and processed paraffin sections may be used but the technique is equally applicable to touch imprints or similar cytological preparations.

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