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FISH / ISH (in situ hybridisation)

aka FISH, ISH, in situ hybridisation, in situ hybridization, fluorescence in situ hybridization, fluorescence in situ hybridisation, break-apart FISH, EBER in situ hybridisation, EBER

A test that uses glowing DNA probes on a tissue slide to count gene copies or spot rearranged genes inside individual cells, used to confirm HER2 amplification, MYCN in neuroblastoma, or ALK and MYC rearrangements.

Fluorescence in situ hybridisation (or chromogenic ISH) shows whether a gene is amplified (extra signals per nucleus, as in HER2 with ratio ≥2.0 or ≥6 copies), deleted (del(17p) in CLL, 1p/19q in oligodendroglioma) or broken and rejoined (break-apart probes for ALK, ROS1, MYC, BCL2, BCL6 in 'double-hit' lymphoma). It works on routine fixed tissue and resolves equivocal IHC 2+ HER2 results. Interphase FISH is standard in myeloma and leukaemia cytogenetics; EBER ISH detects Epstein-Barr virus in tumours. NGS increasingly replaces it for fusions.

Category
Pathology & biomarkers

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