Loss of heterozygosity and microsatellite instability in ductal carcinoma in situ of the breast

To investigate the alterations of genetic instabilities in carcinogenesis o f the breast, we analyzed the allelotypic profile of 65 ductal carcinomas i n situ (DCIS), compared with that of 207 invasive ductal carcinomas (IDC) o f the breast, These studies were performed by means of examining microsatel lite-length polymorphisms at seven loci (AluVpa, ESR, D11S988, D13S267, D16 S398, D17S1159, and D17S855) from microdissected paraffin sections. Allelic loss or imbalance, considered a loss of heterozygosity (LOH), tended to be more frequently seen in IDC than in DCIS, In particular, the frequency of LOH at the 17p locus was significantly higher in IDC than in DCIS (42 vs. 2 3%, P = 0,022). LOH in DCIS was most frequently seen at D16S398 (26%), LOH frequency at D16S398 in low- and intermediate-grade DCIS was higher than th at in high-grade DCIS, while LOH frequencies at D11S988 and D17S1159 in low - and intermediate-grade DCIS was lower than those in high-grade DCIS, LOH frequency at D11S988 in non-comedo type DCIS was lower than that in comedo type DCIS. Furthermore, the frequency of microsatellite instability (MSI) a t only one locus in DCIS (28%) was statistically higher than that in IDC (6 %) (P < 0.001), while there was no difference between the frequency of MSI at multiple loci in DCIS (6%) and that in IDC (3%). Together, these observa tions indicate that chromosomal losses of 16q may occur in low- and interme diate-grade DCIS and those of lip and 17p may occur high-grade DCIS, and th at MSI occurring at only one locus is not yet dear and MSI at multiple loci is uncommon in not only IDC but also DCIS of the breast, (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.