4. Hrvatski kongres kliniËke citologije 4th Croatian Congress ... - Penta

4. Hrvatski kongres kliniËke citologije / 1. Hrvatski simpozij analitiËke citologije / 2. Hrvatski simpozij citotehnologije
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Klinička citologija - Plenarna i pozvana predavanja
for the treatment of patients with GIST whose disease has progressed or who are unable
to tolerate treatment with Imatinib. It is a fact that obtaining an accurate diagnosis
is of utmost importance for a correct treatment, being an earlier diagnosis crucial for
a prompt therapy. Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-
FNA) has been increasingly used for the assessment of diverse intra-abdominal and
intra-thoracic tumors. EUS-FNA not only allows for a meticulous representation of both
extramural and intramural structures of the gastrointestinal tract but also permits tissue
sampling from masses in these locations. Our group was one of the pioneers in
analyze c-Kit mutations in EUS-FNA material. In 2007, we studied eighty-five patients
with intramural gastrointestinal mesenchymal tumors and perform an immunohistochemical
and molecular analysis of both c-kit and PDGFRA genes in formalin-fixed
paraffin embedded cell blocks obtained by EUS-FNA. Cell-blocks of the initial 85 cases
were obtained, however, complete immunocytochemical and molecular analysis was
only possible in 51 cases. The mean age of patients was 62.4 yr (range, 26-92yr). Twenty
(39.2%) patients were females and 31 (60.8%) were males. Topographically, 12 (23.5%)
tumors were located in the esophagus, 35 (68.6%) tumors were gastric and 4 (7.8%)
were located in the small intestine. The mean size of tumors documented by EUS was
33.9mm (range 11-80mm). Immunoreactivity for CD117 was detected in a majority of tumors
pre-classified as GISTs. CD117 positivity in GIST’s tumor cells was strongly present
at the membrane and diffuses in the cytoplasm. CD117 was negative in 7/31 (22.6%)
tumors pre-classified as GISTs. In two cases the immunostaining was not interpretable
due the technical artifacts. PCR amplification and DNA sequencing revealed exon 11 mutation
in 19 (57.6%, 19/33) GISTs, and exon 9 mutation in 1 (3.0%, 1/33) GIST. No PDGFRA
activating mutations were detected in the c-kit wild type bearing tumors. In summary,
our study demonstrates that 77.4% of GISTs strongly and diffusely express kit, irrespective
of topography, age or gender. Albeit several studies indicate that 95-100% of GIST
cases express kit, lower expression levels have been reported in Australian (78%) and
Scandinavian studies (85%). Such differences in protein expression levels are probably
due to distinct methodologies and population diversities. We identified c-Kit mutations
in 61% of GIST cases, in accordance with previously published ranges (30-90%). Nearly
95% (19/20) of c-kit-mutant tumors carried exon 11 mutations.
EUS-FNA, a less costly, less risky, and less invasive strategy is an increasingly used
procedure for the diagnosis of gastrointestinal tumors. In this study, we have shown
that GISTs could be diagnosed pre-operatively on EUS-FNA specimens. In addition to
immunocytochemistry, molecular analysis can be done in formalin-fixed and paraffinembedded
cell block material obtained from these aspirates, avoiding more invasive
diagnostic procedures to obtain a tissue diagnosis.
In nowadays, with two RTK inhibitors available, there is an imperative need in re-defining
GIST diagnosis and including a molecular analysis of both c-Kit and PDGFRA in the current
diagnostic protocol, so as to better and faster establish the specific therapeutic
approach to use in a particular patient. In conclusion, we are unquestionably taking one
step forward in the diagnosis of GIST, by making the molecular analysis routinely feasible
on a small sample.