Predicting the presence of invasive carcinoma from the extent of mammographic malignant microcalcification and grade of ductal carcinoma in situon core biopsy: results from a National Health Service Screening Programme

Four hundred and two cases of malignant microcalcification presenting through a National Health Service screening programme over a 10-year period were analysed. The final histological diagnosis was ductal carcinoma in situ (DCIS) only in 71% (284/402 cases) and DCIS with a focus of invasive disease in 29% (118/402 cases).

There were significant associations with the presence of invasive disease for the histological grade of DCIS (χ² = 9.06, P = 0.003) and for the cluster size (χ² = 12.18, P = 0.0001). The proportion of cases with invasive tumour increased with increasing DCIS grade, from 13% (4/31) for low-grade DCIS to 36% (86/239) for high-grade DCIS; increasing cluster size, from 20% (27/136) <11 mm to 45% (18/40) >60 mm; and with increasing DCIS grade within each microcalcification cluster size category: <11 mm from 13% to 25%, 11 mm to 30 mm from 13% to 36%, 31 mm to 60 mm from 0% to 41%, and >60 mm from 25% to 55% for low-grade to high-grade DCIS, respectively.

The Hosmer–Lemeshow goodness-of-fit test supports this model (χ² = 0.59, P = 0.96). The multidisciplinary team can use these data to estimate the risk of invasive cancer and to formulate appropriate management to minimise the number of patients requiring more than one operation, currently 49% for those with DCIS on core biopsy in a screening population [1].