FISH analysis for Chronic Myeloid Leukaemia
|Specialist Integrated Haematological Malignancy Diagnostic Service (SIHMDS) >> Cytogenetics
FISH involves the application of fluorescent DNA probes specific to genes or genetic regions of interest that highlight abnormalities involving these regions.
In CML the pathogenic chromosome rearrangement is the t(9;22) or its variants, which gives rise to the BCR::ABL1 gene fusion. Conventional cytogenetic analysis is carried out routinely on diagnostic CML samples, in addition to a FISH using BCR::ABL1 probes for the rapid identification of the BCR::ABL1 gene fusion. Further FISH may also be used at the discretion of the laboratory.
In cases of CML, FISH is useful in the following scenarios:
• Rapid identification of BCR::ABL1 at diagnosis or sudden relapse
• Identifying and monitoring BCR::ABL1 aberrations that are cryptic at the level of conventional cytogenetics
• In cases where a sample has failed to produce metaphases, or in which the disease cells are suspected of having failed to divide
• Cases in which only a BM/PB smear is available.
• CML patients in advanced phase often acquire additional chromosomal abnormalities in their BCR::ABL1-positive clone. FISH can be useful in clarifying these aberrations, and monitoring their presence following further treatment.
FISH probes commonly applied to CML samples include, but are not limited to, the following:
MECOM (EVI1) 3q26
Chromosome 8 centromere
|Sample & container required
|A minimum of 2-3mls Bone marrow in lithium heparin.
3-5mls peripheral blood in lithium heparin (if disease cells are present in sufficient numbers to allow cell culture and/or FISH studies, as appropriate)
EDTA PB and BM samples (>1ml) are acceptable for FISH only studies as appropriate. Please note the laboratory does not provide transport medium. Samples sent in transport media from an external laboratory containing Lithium heparin will be accepted if no other media available
|Samples would not be rejected on the basis of small volume, however, 5 mL is ideal.
|Diagnosis: Rapid FISH tests (identification of BCR::ABL1 at diagnosis): 95% should be reported within 3 calendar
Diagnostic karyotype: 14 calendar days
Follow-up: Post treatment follow-up samples are treated as routine; 95% should be reported within 21 calendar days
Relapse/Transformation CML karyotypes: 14 calendar days
If the blood counts are abnormal (high or low white cell count) the volumes of BM/PB requested can be adjusted accordingly. For culture (karyotyping) a WCC of 5×10^6 cells per ml is optimal.