Intratumoral heterogeneity in breast carcinoma revealed by laser-microdissection and comparative genomic hybridization

To evaluate the potential cytogenetic heterogeneity in breast carcinoma, several small cell groups (each consisting of 20 to 50 cells) were investigated within paraffin sections. BE laser-microdissection, three to seven cell groups rt ere taken per case. The DNA was amplified by degenerate oligonucleotide primed PCR (DOP-PCR) and the samples tr ere analyzed by CGH for chromosomal gains and losses. Two ductal invasive breast carcinomas, one of them with two lymphnode metastases, rr ere investigated. To compare the results from the small samples, CGH was also performed on DNA isolated from the tumorous regions of three to five serial sections (10(7) to 10(6) cells). The aberrations observed in the microdissected tumor samples were multiple and involved up to 14 different chromosomal or subchromosomal regions. The most frequent changes were gains on chromosomes lag (14/20) and 20q (16/20), and loss on 13q (12/20). Some aberrations have rarely been detected (e.g., loss on 2p, gain on 8q). Comparing chromosomal imbalances in primary tumors and lymph node metastases, more consistent changes rr ere found between the primary tumor and its corresponding metastases than between both primary tumors. The laser-microdissected samples in general showed more chromosomal aberrations than DNA isolated from several tumor sections. Our CGH results ri ere confirmed by fluorescence in situ hybridization (FISH) for the chromosomal regions of centromere 1 and 20, and 20q13. In addition, microsatellite analyses on 31 samples confirmed our CGH findings for selected chromosome regions 2p and 11q. If cc-m be concluded that there is a distinct intratumoral heterogeneity in primary breast tumors as well as in the corresponding lymph node metastases. The combination of microdissection and CGH enabled us to detect cytogenetic aberrations from important clones which are missed rr hen analyzing DNA extracted from large cell numbers. (C) Elsevier Science Inc., 1999. All rights reserved.