Andrew H. S. Lee

Aims The method of diagnosis of ductal carcinoma in situ (DCIS) has changed since the 1980s. The aim of this audit was to assess changes in the preoperative diagnosis of DCIS since the introduction of needle core biopsy, particularly the proportion with a preoperative biopsy diagnosis of DCIS. Methods and results The preoperative diagnoses of patients with a final diagnosis of DCIS in the surgical specimen were reviewed (i) in 809 patients who presented through breast screening from 1997 to 2021, and (ii) in all patients in 5 individual years at 5‐year intervals from 2000 to 2020 (254 in total). For screening‐detected DCIS the proportion with a preoperative diagnosis of DCIS increased from 75% to 98% over the study period. In a detailed analysis of all cases of DCIS in 5 separate years the proportion with a preoperative diagnosis of DCIS increased from 68% in 2000 to 96% in 2020. For high‐grade DCIS the proportion increased from 87% to 97%, and for low‐ or intermediate‐grade DCIS from 48% to 93%. The proportion of women who had vacuum‐assisted biopsy increased from 7% in 2000 to 58% in 2015. There was a small increase in the number of biopsies that had basal cytokeratin and oestrogen receptor immunohistochemistry to aid diagnosis. Conclusion There has been an increase in the preoperative diagnosis of DCIS, particularly of low‐ or intermediate‐grade, over the last two decades. The increasing use of vacuum‐assisted biopsy is likely to be a major contributory factor to this increase.