Abstract: | The “marriage of cytology and cytogenetics” has recently
been celebrated, as reported by Dal Cin et al.
(Cancer Cytopathol, 2013). To make it a long-lasting
marriage, however, it is important to set new DNA
FISH probes, targeting specific DNA regions involved
in changes (gene loss, amplification, gene fusion) in
various tumors. Differentiated thyroid cancer accounts
for more than 80 % of all thyroid cancers, and is
represented by papillary thyroid carcinoma (PTC)
and follicular thyroid carcinoma (FTC) histotype variants.
Expanding knowledge on the molecular pathways
implicated in their pathobiology has revealed
that several gene changes play a cogent role in the
pathogenesis of these carcinoma: BRAFV600E mutation,
rearrangements of the tyrosine kinase receptor
genes RET and TRK, and RAS mutations are mutually
exclusive in PTC (found in more than 70 %), whereas
RAS mutations or PPARg fusion mutations (PAX8-
PPARg and CREB3L2-PPARg), also mutually exclusive,
are identified in up to 75 % of FTC. On these
bases, the use of some of these abnormalities as tumor
biomarkers is becoming part of clinical practice, and
their preoperative examination is increasingly being
used as an adjunct to cytology. Eco-guided fine needle
aspiration is a precious source of pre-operative material,
in which the presence of RET-PTC variants and
PPARg fusion mutations might be tested using FISH.
To optimize the use of this material, simultaneously
studying RET and PPARg genes integrity - in a single
FISH experiment - is mandatory. To pursue this aim,
we designed a tetra-color break-apart cocktail probe,
containing 5′ and 3′ flanking sequences of each gene,
using four different fluorophores: SpectrumGreen and
SpectrumGold for RET and SpectrumAqua and
SpectrumRed for PPARg. The probe was able to correctly
identify RET and PPARg breakage in samples positive for
RET/PTC and PAX8/PPARg rearrangements assessed
by RT-PCR.
Supported by the Banco Sardegna Foundation. |