Ductal carcinoma in situ in core biopsies containing invasive breast cancer: correlation with extensive intraductal component and lumpectomy margins.

Background And Objectives: The diagnosis of invasive breast cancer is most commonly made on image-guided core biopsy (CB). The presence of extensive intraductal component (EIC), as identified on subsequent lumpectomy, is associated with an increased risk of positive margins and need for further surgery. CBs demonstrating invasive breast cancer may also contain ductal carcinoma in situ (DCIS), although the significance of this finding is unclear. The objective of this study was to examine the implications of DCIS found in the original CB, specifically related to the risk of EIC and/or positive lumpectomy margins.

Methods: All patients at a single academic institution who underwent initial breast conserving surgery for invasive breast cancer diagnosed on image-guided CB between 05/00 and 04/02 were included in the study. A systematic, blinded review of all CB and lumpectomy specimens was performed using standardized criteria for DCIS, EIC, and margins.

Results: A total of 95 patients were included in the study, with a mean of 5 (median 5) CB/patient. Of these, 43 (45%) patients had DCIS identified in their CB; in 34 (79%) of these patients, the DCIS was mixed with the invasive cancer. No differences in tumor size or lumpectomy volume were identified between patients with or without DCIS on CB. However, patients with DCIS were noted to be significantly younger. Overall, EIC was identified in 13 (14%) patients; the risk of EIC was significantly higher in patients with DCIS identified in CB than in those with invasive carcinoma alone (30% vs. 0%, respectively; P < 0.0001). Expectedly, the incidence of positive margins on lumpectomy was higher in patients with EIC (38% vs. 16%; P = 0.05). A trend, although not statistically significant, towards positive margins was also noted in patients with DCIS on CB compared to those with invasive carcinoma alone (24% vs. 15%, P = 0.3).

Conclusions: The identification of DCIS in conjunction with invasive cancer on CB appears important; the absence of DCIS in a CB sample excludes the possibility of eventually identifying EIC. Knowledge of DCIS in CBs with invasive carcinoma may be helpful for surgeons in planning gross resection margins at lumpectomy.