Fish analysis

Acronym for "fluorescence in situ hybridization".

Cytogenetic method, which is mainly used in prenatal and carcinoma, leukemia and lymphoma diagnostics. In FISH analysis, one or more probes labelled with a fluorescent dye are hybridised directly to the nuclear DNA. In this way, conventional chromosome staining can be used to detect changes that are often not visible. By means of FisH analysis, numerical and structural changes in the chromosomes (e.g. the sex chromosomes X and Y) can be detected relatively reliably (such as Ullrich-Turner syndrome - monosomy X-, or Klinefelter syndrome).

Other chromosomal aberrations such as triploidy or tetraploidy, trisomy (e.g. in Down's syndrome - trisomy 21-) are also detected.

Furthermore, a large number of chromosomal changes (e.g. in malignant lymphomas) can be detected, e.g. different chromosomal alterations in the brain. translocations (e.g. translocation t(13;14) in nodal germinal lymphomas ( lymphoma, cutaneous B-cell lymphoma, germinal lymphoma) as well as the amplification of the her2/neu gene in breast carcinoma and its metastases. The FISH analysis is also used in the diagnosis of childhood leukaemia.

The great advantage of FISH compared to other techniques is that FISH also works on formalin-fixed tissue. In addition, the method analyses individual cells of a tissue network and thus also enables the breakdown of existing tumour heterogeneity.

1. Hallermann C et al (2004) Molecular cytogenetic analysis of chromosomal breakpoints in the IGH, MYC, BCL6 and MALT1-gene loci in primary cutaneous B-cell-lymphomas.J Invest Dermatol 123: 213-219