In this study, we compared the gene amplification frequencies of HER2, C-MYC, CCND1 and FGFR1 in a relatively large series of pure DCIS, DCIS associated with invasive carcinoma, and invasive carcinomas, to investigate the role of gene amplification in the progression of DCIS to invasive carcinomas. The gene discussed is FGFR1; the disease is ductal breast carcinoma in situ.