ABSTRACT
Despite debates about the quality and validity of the randomized trials on breast cancer screening 1,2 , it is generally accepted that mammography screening will lead to a breast cancer related mortality reduction of about 15% (10-30%) in the screened population 3 . Screen-detected breast cancers are usually smaller, lower grade and less frequently associated with lymph node involvement as compared with clinically detected breast cancers, resulting in better survival rates. Even in comparable stages, screen-detected breast cancers appear to have a better outcome than non-screen-detected cancers 4-8 . Furthermore, about 15-20% of screen-detected breast cancers are in situ carcinomas, predominantly ductal carcinoma in situ (DCIS) 9,10 . It is suggested that screening-detected breast cancers have different biology. Interval cancers do have much more similar clinicopathological features and consequently biological behavior to clinically detected breast cancers as compared with screening-detected cancers 11 .
