Can preoperative factors predict for residual malignancy after breast biopsy for invasive cancer?

The presence of malignancy at the resection margins of a malignant breast biopsy requires difficult therapeutic decisions about whether a re-excision biopsy is necessary. The aim of this study was to determine the factors predisposing to the involvement of the resection margins in 280 women undergoing breast biopsy for invasive malignancy from a single breast screening practice. Resection margins were assessed independently by a single pathologist who noted either the presence of tumour at the margins of the biopsy specimen or in the shavings taken from the biopsy cavity. Resection margin involvement (RMI) occurred in 113 patients. Mammographic microcalcification (MM) was seen in 87 women with invasive cancer and RMI occurred in 53 (61%) compared with 60/193 invasive cancers without MM (P < 0.001). If RMI was present the patients underwent a second procedure to ensure complete tumour excision, and 68% of re-excision specimens from tumours with MM and 36% of tumours without MM contained residual malignancy (P < 0.005). Statistical analysis demonstrated that these observations were independent of tumour size, grade, type, and axillary node status. The presence of mammographic microcalcification therefore indicates that wider than usual surgical resection margins should be taken.