Molecular Cytogenetics (FISH)

FISH (fluorescence in situ hybridization) is a molecular cytogenetic method based on the binding of fluorescently labeled DNA probes to genetic material within cells. It shows, in a targeted manner, small losses and gains (microdeletions/microduplications) beyond the resolution of conventional karyotyping, as well as specific chromosomal rearrangements.

Because the method uses probes specific to defined target regions, it is used not as a replacement for methods that examine all chromosomes, such as karyotyping and sequencing, but as a complementary test that assesses targets selected according to the physician's clinical suspicion.

When is it used?

Targeted assessment when microdeletion/microduplication syndromes are suspected (e.g. 22q11.2 deletion, Prader-Willi/Angelman regions, Williams syndrome region)
Confirmation of translocations, inversions and deletions identified by karyotyping or highlighted by clinical suspicion
Fusion and enumeration analyses supporting the physician's diagnostic and follow-up decisions in hematological diseases (e.g. BCR::ABL1)
Rapid aneuploidy assessment for chromosomes 13, 18, 21, X and Y in prenatal and postnatal samples

Sample types

FISH analysis can be applied to peripheral blood, bone marrow, amniotic fluid, CVS (chorionic villus sampling) and various tissue samples. The appropriate sample type and probe set are determined by the requesting physician's clinical assessment.

Stages of the analysis

Physician request and sample acceptance

Sample preparation and hybridization of the labeled probe

Signal evaluation under a fluorescence microscope

Preparation of the report and delivery to the requesting physician

Important notice

FISH assesses only the region targeted by the probe; it does not screen the whole genome. Results must be interpreted by a physician, together with karyotyping and other molecular test findings. This page is for informational purposes about the method and does not establish a diagnosis on its own.