Fluorescence In-Situ Hybridization (FISH) is a sensitive, specific, reliable and fast method for identifying chromosomal changes that support diagnosis and patient management.
Where FISH is used
Blood cancers
CML, ALL, AML and multiple myeloma.
Solid tumours
Breast and lung cancer, neuroblastoma and Burkitt lymphoma.
Birth defects
Suspected genetic disorders such as Down syndrome, before and after birth.
Rapid results
Usually within 24 hours through an overnight procedure.
Advantages of the FISH technique
- Rapid detection: works on non-dividing (interphase) cells, so results are usually available within 24 hours.
- Flexible sample types: fixed cells from blood or bone marrow, blood and marrow smears, touch preparations and formalin-fixed paraffin-embedded (FFPE) sections.
- Fine-scale detection: reveals submicroscopic microdeletions and hidden (cryptic) balanced or unbalanced translocations, even in interphase cells.
Methodology
DNA probes (BAC/PAC clones) for a target gene are labelled with fluorescent dyes and hybridised to the patient sample. Under a fluorescence microscope, the coloured signals show whether a gene is present, missing, amplified or fused.
Example: BCR-ABL in chronic myeloid leukaemia (CML)
Metaphase FISH detects the BCR-ABL gene fusion. In interphase cells from a CML patient, a specific signal pattern (one fusion, two red, one green) confirms the result.
Why HER2/neu FISH testing matters
The HER2 gene (ERBB2) is amplified or overexpressed in roughly 20–25% of invasive breast cancers. HER2 status is the main factor in deciding eligibility for trastuzumab, an effective targeted therapy that works only for patients whose HER2 FISH result is positive.
