The Principles of Clinical Cytogenetics - Extra Materials - Springer

470 Daynna Wolff and Stuart Schwartz
Fig. 9. Examples of normal (column A) and abnormal (column B) results for hematologic malignancies
with various FISH probe types. The probe type and a chromosomal abnormality exemplifying typical results
are given.
with atypical FISH patterns, including those with a deletion on the derivative chromosome 9 (47).
Among these patients, there is loss of a portion of BCR or ABL1 or both of these hybridization sites
normally associated with the break and fusion point on the abnormal chromosome 9.
The loss of DNA associated with the break and fusion point on chromosome 9 in cells with a
t(9;22)(q34;q11.2) is associated with a relatively poor prognosis and reduced response to treatment
(48–50), with average long-term survival reduced from 88 months to 38 months. FISH is the optimal
methodology for the detection of this clinically relevant deletion, as it is not visible with
routine cytogenetics. An additional probe (for the argininosuccinate synthetase gene [ASS] at 9q34)
is often utilized to eliminate the possibility of false positives (see Fig. 10) (51). Alternatively, use
of the four-color, dual-signal exchange probe set allows for definitive identification of deletions
and other unusual rearrangements involving the derivative chromosomes (see Fig. 11d, e).