ABSTRACT
Nearly all breast cancers have an intraductal origin, and as long as a cancer remains inside the ductal system, mammography may only reveal it by the presence of microcalcifications. It is when an intraductal cancer becomes invasive that it will often appear as a mass in a mammogram. In this phase it should be detected as small as possible, because tumor size is a very important prognostic factor (1). Consequently, the success of breast cancer screening programs critically depends on the ability to detect nonpalpable invasive cancers, ideally when they are smaller than 1.5 cm, because only these are detected early enough to have a strong impact on overall mortality reduction. Masses smaller than 5 mm are rarely visible in mammograms, and detection of intraductal in situ cancers is less effective, because many of these do not get invasive during lifetime.
