Although biological, this is probably more accurately described as a "high-level polysomy
" rather than true gene amplification; the definition, nonetheless, correlates strongly with clinical outcome, including therapeutic response to tyrosine kinase inhibitors (20).
8 is one of such rare karyotypic abnormalities that define a distinct biological subgroup of myeloid hematopathologies.
Since chromosome 17 polysomy
can lead to false-positive results, it should be taken into consideration during identification, and evaluation of this entity.
Low-grade duplication of H2N gene (3 to 4 copies/cell) is usually the result of chromosome 17 polysomy
and is not usually in association with high-level overexpression.
Interestingly, a significant number of cases (21 of 28, 75%) ultimately reclassified into the HER2 FISH equivocal group exhibited an average CEP17 copy number of 3 or greater, which is the traditional cutoff used to define chromosome 17 polysomy
. This proportion was much higher (17 of 49, 34.7%) as compared to cases ultimately reclassified as HER2 FISH positive with a concurrent CEP17 copy number of 3 or greater.
(8.) Fryns JP, Kleczkowska A, Petit P, van den Berghe H.X-chromosome polysomy
in the female: personal experience and review of the Literature.
The definition of KS, as an inclusion criterion for this study, required the availability of a karyotype consisting of an X chromosome polysomy
and at least one Y chromosome, either as a single lineage or as a mosaicism (7).
Angiomatous meningiomas have a distinct genetic profile with multiple chromosomal polysomies including polysomy
of chromosome 5.
Furthermore, high polysomy
or gene mutation has been reported to play a role in EGFR overexpression in non-small-cell lung cancers and in breast cancer [31-33].
They also observed polysomy
of chromosomes 3, 4, 10, 13, 17, and 18 in one case.
poses another dilemma in interpreting HER2 FISH results; in addition, an increased number of CEP17 signals are related to amplification of the centromeric region rather than to true polysomy
Caption: Figure 6: FISH analysis of resected abdominal mass: dual color probe (ZytoLight KRAS/CEN 12), demonstrating polysomy
and isochromosome 12p (CEN 12: red; KRAS: green); magnification 1000x.