20q13.2 Amplification in intraductal hyperplasia adjacent to in situ and invasive ductal carcinoma of the breast

The 20q13 region harboring recently described putative oncogenes is frequen tly amplified in invasive ductal carcinoma (IDC). The aim of this study was to examine the 20q13 copy number in intraduct hyperplasia (IH), atypical d uct hyperplasia (ADH), and ductal carcinoma in situ (DCIS) adjacent to IDC. In 5 patients, comparative genomic hybridization (CGH) after laser microdi ssection revealed 20q13 amplification in four of five cases of IH, in all o f three cases of IH with atypia, all five of DCIS, and all five of IDC. Flu orescence in situ hybridization (FISH) confirmed the amplification at 20q13 .2 in IH in the two specimens analyzed. The amplification rate, however, wa s higher in DCIS and IDC. In phenotypically normal ductal epithelium normal values were found for 20q13 copy number by FISH (n=2) and CGH (n=5). Altho ugh the number of cases presented here is small, our results suggest that m utations in the 20q13.2 region in IH may be associated with accelerated pro liferation and hyperplasia of the ductal epithelium. Progression to DCIS an d ICD is accompanied by a further increase in the 20q13.2 copy number.