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6th ESACP Congress, Heidelberg, April 7-11, 1999 |
A154
Most breast cancers are known to have considerable amounts of stromal cells
as fibroblasts (desmoplasia) and mononuclear cells. Analysis of tumor-
specific genetic alterations can be compromised by the presence of these
normal cells, requiring microdissection of pure tumor cell areas for reliable
detection of loss of heterozygosity (LOH) and microsatellite instability
(MSI). Normal breast tissue and primary breast tumor samples of 40 patients
were analyzed for MSI and LOH by polymerase chain reaction followed by
polyacrylamide gel electrophoresis and silver staining using 16
microsatellite markers on ten chromosomes. Pure tumor cell populations were
obtained using either manual or laser capture microdissection (PALM) of
methylenblue stained paraffin-embedded tissue as well as archived
hematoxylin/eosin stained slides and the results of both techniques were
compared. Tumor cells of histopathologically heterogeneous areas in each
tumor (i.e. scirrhous and intraductal components) were processed separately.
Regions of special interest were captured with a digital camera device
before microdissection, allowing an accurate assignment of genetic
alterations to the histologic phenotype. The following results were
obtained: 1) accurate microdissection of tumor cells revealed a higher
frequency of MSI-positive breast-cancers as previously reported in
literature 2) laser microdissected samples showed a significantly higher
frequency of MSI-and LOH-positive tumors than the manually ones due to
reduction of contamination by desmoplasia 3) MSI-positive tumors showed
a high degree of intratumoral heterogeneity. Laser based microdissection
is a valuable tool in genetic analysis of desmoplastic tumors and allows an
accurate determination of genetic alterations in histologically different
tumor regions.
LASER MICRODISSECTION OF BREAST CANCER FOR DETERMINATION OF MICROSATELLITE
INSTABILITY AND TUMOR HETEROGENEITY
Wild P, Hofstädter F, Dietmaier W, Hartmann A
University of Regensburg Medical School, Department of Pathology and
Molecular Diagnostic Unit, Franz-Josef-Strauß-Allee 11, 93042 Regensburg