The present study aims to assess the influence of lesion size on the radiological features of screen-detected ductal carcinoma in situ (DCIS) in Sloane Project cases.

Cases where calcification was present mammographically, and histological grade and size were available, were included. Calcific DCIS was classified radiologically as casting/linear, granular/irregular or punctate. The pathology dataset included tumour grade and size. Correlations were sought between the radiological and pathological findings and significance assessed.

A total of 1,783 cases were included. Of these, 1,128 women, 485 women and 170 women had high-grade, intermediate-grade and low-grade DCIS, respectively. Casting calcification was more frequently seen the higher the tumour grade; occurring in 58% of high-grade, 38% of intermediate-grade and 26% of low-grade cases, respectively (P < 0.001). However, casting calcification was also increasingly common with increasing size, irrespective of grade (P < 0.001). Thus casting calcifications in small (<10 mm) high-grade DCIS were seen with a similar frequency (50%) to those in moderate-sized (21 to 30 mm) intermediate-grade lesions (48%) and to those in large (>30 mm) low-grade lesions (46%).

Lesion size has a strong influence on the radiological features of calcific DCIS; small high-grade lesions often show no casting calcifications, while casting calcifications are seen in approaching one-half of large low-grade lesions. The radiological appearances alone cannot be used to predict the histological grade of DCIS.