FISH, CISH, testing, in situ hybridization, services, cytogenetics – Melbourne Victoria Australia

FISH and CISH

FISH & CISH (in situ hybridization) Services

In Situ Hybridization (ISH) can be used to detect several different kinds of chromosomal and genetic abnormalities:

Chromosomal abnormalities that are too small to detect microscopically
Chromosomal abnormalities in cells where the chromosomes are compacted and too small to see microscopically (e.g. interphase cells, including interphase cells in formalin-fixed, paraffin-embedded tissues prepared for histopathological examination)
To define the origin of microscopically-visible but complex chromosomal abnormalities, for example, translocations.
To assess microscopically-visible chromosome number or integrity more rapidly (hours) than can be achieved with karyotyping (days).

TissuPath's Division of Cytogenetic Services provides full ISH services at the highest international standard. Our laboratory is fully NATA-accredited for FISH, and all our senior cytogeneticists are HGSA-qualified.

In simple terms, ISH uses molecular probes which bind to specific regions of chromosomal DNA. The probes are "tagged" with molecules that allow the probes to be visualized in cells by either fluorescence when exposed to light (Fluorescent In Situ Hybridization, FISH) or by causing the precipitation of colored crystals near the probe (Chromogenic In Situ Hybridization, CISH).

FISH provides very specific information about the presence or absence of specific chromosome regions, since normals will have two fluorescent dots (since chromosomes come in pairs) while abnormals will have either less or more than two signals. CISH [link to popup double photo of breast cancer showing amplified and non-amplified HER-2/neu gene] is less quantitative, but is useful for detecting amplification (an increase in the number) of specific genes.

Click here to learn more about how ISH works.

ISH can be used on all preparations of cells and tissues including formalin-fixed, paraffin-embedded tissues (i.e. those suitable for histopathologic examination) to assess gene and chromosome integrity.

When would ISH be used?

TissuPath's cytogeneticists and pathologists use ISH frequently for the following indications:

During a pregnancy, when it is possible to sample the baby’s cells (either chorionic villi sampling (“CVS”) or amniocentesis (“amnio”) to determine, more rapidly than is possible by karyotyping, if the baby has a specific chromosome abnormality, such as Down Syndrome (trisomy 21)
In certain types of brain tumours, to determine whether there are specific chromosomal deletions which affect the prognosis and the tumours response to cancer chemotherapy. TissuPath has played a leadership role in implementing FISH testing for oligodendrogliomas in Australia.
For breast cancers, to determine whether the Her-2/neu gene is "amplified" (more than the normal two copies/cell), which suggests that the tumour will be responsive to trastazumab (Herceptin®). TissuPath is certified for CISH testing of breast cancer [link to popup photo with legend] specimens by NATA and Vysis.