96. Jahrestagung der Deutschen Gesellschaft für Pathologie e. V ...

aims are twofold: 1) to verify the immunohistochemical expression of
ETV1 in a large series of mesenchymal tumors of the gastrointestinal
tract; 2) to verify its possible relationship with clinicopathologic parameters
(risk classification, survival, mutational status).
Methods. 424 GISTs (381 primary and 43 metastases), 30 leiomyomas,
8 leiomyosarcomas and 1 schwannoma in TMA format. Mean age was
66±1.4 ys. For the risk classification was used the schema of Miettinen
in 5 groups (probably benign,18%, very-low risk, 17%, low-risk, 14%, moderate
risk, 12% high-risk, 10%) adding overtly malignant tumors, 20%
and metastases, 9%. Immunohistochemical staining for ETV1 (AbCam®,
dilution 1:100) was performed. Immunoreactivity was scored by evaluating
the number of positive nuclei over the total number of tumor cells.
For survival analysis the series was dycotomised, using 0 as cut-off.
Results. ETV1 was expressed in the majority of primary GISTs (76% of
cases) and of metastases (86%), but also in leiomyosarcomas (50%) and
in leiomyomas (38%). The maximum score was observed in metastases
(mean 68%) and in primary GISTs (mean 48%). Leiomyosarcomas (mean
37%) and leiomyomas (mean 14%) had a lower score. The differences were
statistically significant (0.0001T) being the most frequent, as well as 8 deletions, and 5 deletion-insertions.
CGH revealed -14q, -1p, and -22q as most the common
aberrations (39, 15, and 10 cases, respectively). The mean number of clonal
net changes was 2.68 (0.6 gains, 2.1 losses), and 10 tumors revealed no
chromosomal imbalances.
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