Differences in genetic alterations between primary lobular and ductal breast cancers detected by comparative genomic hybridization

Infiltrating ductal (DC) and lobular carcinoma (LC) of the breast represent the most frequently observed varieties of invasive breast cancer, characte rized by differences in their histological and clinical properties. Althoug h comparative genomic hybridization (CGH) of invasive breast carcinomas has revealed a complex and consistent pattern of DNA copy number changes, the data with regard to type specific aberrations are limited. A comprehensive study was therefore performed on 19 LCs and 29 DCs to ascertain type-specif ic differences of unbalanced DNA copy number changes blv CGH. Statistical a nalysis revealed significantly higher frequencies for underrepresentation o f chromosomes 16q (p < 0.01), 22 (p < 0.05), and 17q (p < 0.05), and a lowe r frequency for overrepresentation of chromosome 8q (p < 0.01) in LC. Simil ar frequencies of nonrandom chromosomal changes in LC and DC were obtained for gain of Iq (74%/59%) and loss of 19p (53%/52%), parts of Pp (42%/41%) a nd 11q (21%/24%). Less frequently; gains mainly involving parts of chromoso mes 20q, 20p, 3q, and 5p and partial losses of chromosomes 17p and 13 were observed in both groups of tumorus. Minimal regions of overlapping amplific ations mere mapped to 17q23 exclusively in DC (17%) and 11q13-q14 in both D C and LC (21% and 11%, respectively). High occurrences of DNA copy number d ecreases were detected at the distal part of chromosomes Ip, 19 and 22, but further analysis is required to confirm these imbalances. It is suggested that the observed differences are involved in the development of type-speci fic properties of DC and LC. Copy-right (C) 2000 John Wiley & Sons, Ltd.