Heterogeneous chromosomal aberrations in intraductal breast lesions adjacent to invasive carcinoma

There is evidence that breast cancer is a heterogeneous disease phenotypica lly as well as molecular biologically. So far, heterogeneity on the molecul ar biological level has not been investigated in potential precursor lesion s, such as ductal hyperplasia (DH) and ductal carcinoma in situ (DCIS). In this study we applied comparative genomic hybridization (CGH) to formalin-f ixed, paraffin-embedded breast tissue with DH and DCIS, adjacent to invasiv e ductal carcinoma (IDC), to screen these potential precursor lesions for w hole genomic chromosomal imbalances. Laser-microdissection was used to sele ct pure cell populations from the sections. Isolated DNA was amplified by d egenerate oligonucleotide primed PCR (DOP-PCR) and further processed for CG H analysis. Investigating multiple samples (n=25) from four patients we found an averag e of 5.6 +/- 0.9 (mean +/- SEM) chromosomal imbalances already present in D H. In the twelve DCIS lesions an average of 10.8 (+/- 0.9) aberrations was identified with 14.8 (+/- 0.8) aberrations in the four adjacent IDC lesions . The increasing number of chromosomal changes in parallel with the histopa thological sequence corroborate the hypothesis, that the carcinomas may hav e developed through a sequential progression from normal to proliferative e pithelium and eventually into carcinoma. However, heterogeneous results wer e identified in the multiple samples per entity from the same patient, demo nstrated mainly in the DCIS samples in the chromosomal regions 6p, 9p, 11q, 16p and 17q, in the DH samples by 3p, 16p and 17q. This heterogeneous find ings were most pronounced within the DH and was less in the DCIS and IDC sa mples. The only aberration consistently found in all samples - even in all DH samples - was amplification of the 20q13 region. Our results demonstrate, that the applied combination of laser-microdissect ion, DOP-PCR and CGH, may serve to analyse breast carcinogenesis pathways i n suitable histological material. However, so far, it is unclear how to han dle heterogeneous results and these make identification of relevant changes more difficult. Setting a threshold and valuating only those chromosomal c hanges which are present in a majority of samples may be one possibility. T his involves however, the risk that infrequent but possibly significant abe rrations may be missed. Figures on http://www.esacp.org/acp/2000/20-1/aubele.htm.