Objective To explore how the number and type of breast cancers developed after screen detected atypia compare with the anticipated 11.3 cancers detected per 1000 women screened within one three year screening round in the United Kingdom.
Design Observational analysis of the Sloane atypia prospective cohort in England.
Setting Atypia diagnoses through the English NHS breast screening programme reported to the Sloane cohort study. This cohort is linked to the English Cancer Registry and the Mortality and Birth Information System for information on subsequent breast cancer and mortality.
Participants 3238 women diagnosed as having epithelial atypia between 1 April 2003 and 30 June 2018.
Main outcome measures Number and type of invasive breast cancers detected at one, three, and six years after atypia diagnosis by atypia type, age, and year of diagnosis.
Results There was a fourfold increase in detection of atypia after the introduction of digital mammography between 2010 (n=119) and