What is the value of detecting ductal carcinoma in situ at mammographic screening?
The introduction of mammographic screening has led to a dramatic increase in the number of cases of pure DCIS diagnosed. Of screen-detected breast cancers 25% are DCIS, as compared with 5% of symptomatic breast cancer [8,9]. Screening of women who are under 50 years of age identifies even higher proportions of DCIS lesions than are seen when screening women older than 50 years [10]. Critics of breast screening often claim that the high rates of DCIS seen represent over-diagnosis, many being lesions that would never present clinically and threaten the woman’s life. This is compounded by the fact that such lesions may be extensive and therefore frequently require mastectomy to obtain adequate excision. Such criticism would be valid if screen-detected DCIS lesions were predominantly of low histological grade. However, DCIS detected by mammographic screening is predominantly of high nuclear grade and only 13% is low grade [11]. Screen-detected DCIS is also more likely to contain areas of n
