Factors affecting surgical margin clearance in screen-detected breast cancer and the effect of cavity biopsies on residual disease.

One hundred and fourteen localization biopsies for screen-detected breast cancers were assessed for surgical margin clearance and presence of tumour in the cavity biopsies or subsequent resections. Inadequate surgical clearance (< or = 1 mm from the margin) in 88 patients was associated with high nuclear grade ductal carcinoma in situ, or extensive in-situ change accompanying invasive carcinomas, vs pure invasive carcinomas. Smaller localization biopsies (< or =50 g), larger tumours, and absence of a definite fine-needle aspiration cytological diagnosis of malignancy were also associated with inadequate excision. The radiographic characteristics of the tumours did not correlate with inadequate excision. Sixty-five patients had cavity biopsies taken at the time of surgery and 23 (35%) biopsies were positive, 20 of which were associated with incompletely excised tumours. Further excision in 78 patients yielded residual disease in 63%, most of whom had had inadequate surgical clearance. When cavity biopsies were taken with incompletely excised tumours, 15 of 88 subsequent resection specimens harboured residual disease compared with 29 of 88 without cavity biopsies. Although cavity biopsies increase the clearance margin, a negative cavity biopsy is not always an assurance of adequate excision.