Sarcomatoid differentiation has been associated with molecular changes with advanced polysomy
of chromosomes 3 and 16, trisomy 9, and loss of Y chromosome, (12) monosomy of chromosomes 3, 9, and 16, (24) and loss of chromosomes 1p, 2q, 9, and 14.
Among the positive specimens, seven exhibited EGFR gene amplification and 13 exhibited high polysomy
of EGFR gene.
Role of polysomy
17 in transitional cell carcinoma of the bladder: immunohistochemical study of HER2/neu expression and fish analysis of c-erbB-2 gene and chromosome 17.
Several studies reported that the development of resistance to anti-EGFR therapies was associated with acquired gains of KRAS that occurred either as novel focal amplifications or as high-level polysomy
of chromosome 12p (60, 61) and that resistant clones in the circulation were detectable months before progression was clinically obvious (60, 62).
Furthermore, after G-banding the most frequent engagement in polysomy
was of the X chromosome.
In order to avoid misinterpreting chromosome 17 polysomy
as HER2 gene amplification, the use of a CEN 17 probe is recommended for more accurate HER2 status assessment.
In-situ hybridization using probes for highly repeated sequences located in the centromere regions of specific chromosomes was then used on tissue sections of these specimens to detect chromosome polysomy
, or the presence of cells with three or more chromosome copies.
7 chromosome 17 per nucleus on average were considered as polysomy
In addition, polysomy
17 was noted in 25 cases, of whom 14 were amplified, nine were not amplified and 2 were equivocal.
It is worth noting that Stevens suggested a possible relationship between the Bs and the X, which is presently considered as one of the possible origins of Bs through polysomy
and degeneration (Hewitt 1976, Camacho et al.
A recent report which may ultimately resolve the conflicting data discussed above is the description by Bartlett at the 2008 San Antonio Breast Cancer Conference of an association between polysomy
17 and benefit from anthracyclines in the UK NEAT trial .
Also, colorectal tumours distinguishable by fluorescence in situ hybridisation (FISH) analysis of EGFR as homogeneously disomic or with low chromosome 7 polysomy
have a reduced response rate to panitumumab .