Introduction

Ductal carcinoma in situ (DCIS) is predominantly an asymptomatic disease detected by mammographic screening. Twenty-one percent of cancers diagnosed by the National Health Service Breast Screening Programme (NHSBSP) in 2006–7 were non-invasive. The number of DCIS cases diagnosed by the NHSBSP has more than doubled in the last 10 years with 3300 cases diagnosed in 2006–7.

The proportion of screen-detected tumors that are DCIS varies according to the age of the population screened and also the threshold of the film readers regarding the recall of mammographic calcification, calcification being by far the commonest radiological feature of DCIS. Calcifications associated with DCIS can be comedo (rod-shaped or branching), granular (like sugar grains), or round or punctate. The frequency of these types of calcification in Sloane Project DCIS cases is shown in Figure 7.1. About half the DCIS cases manifesting as calcification show comedo calcification while DCIS uncommonly shows only punctate calcification with no granular or comedo forms. Younger women have a higher proportion of DCIS detected at screening compared with older women (Figure 7.2), and women are more likely to have DCIS diagnosed on their first screen than on subsequent screens (Figure 7.3). Younger women are also more likely to have an extensive in situ component associated with an invasive cancer than older women. This is why calcification is a more important mammographic feature of malignancy, the younger the screening population.