Lumpectomy margins are affected by tumor size and histologic subtype but not by biopsy technique

The effect of the type of biopsy (needle vs. excisional) on lumpectomy margin status has not been well established. The objective of this study was to determine whether needle biopsy is associated with a higher positive margin rate at time of lumpectomy. We evaluated this hypothesis in the setting of a prospective multi-institutional study. A total of 3975 patients were enrolled in the University of Louisville Breast Cancer Sentinel Lymph Node Study from May 7, 1998 to June 3, 2003. Patients who underwent lumpectomy at the time of their sentinel lymph node biopsy were the focus of this analysis. Patients with clinical stage T1 N0 and T2 N0breast cancer were eligible; 29 patients were found to have T3 tumors on final pathology. Pathologists at each institution defined margin positivity, and tumor at the inked margin of resection was the study guideline. Median patient age was 59 years, and median tumor size was 1.5 cm. A total of 2658 patients underwent lumpectomy with the following results. The cancer of 1515 patients was diagnosed by fine-needle or core-needle biopsy and of 821 patients was diagnosed by excisional biopsy; in 322 patients the method of diagnosis was unknown. The type of previous biopsy did not significantly affect the positive-margin rate at the time of lumpectomy (13.3% vs. 11.0% for needle and excisional biopsy, respectively, P = 0.107). However, patients with larger tumors were more often found to have a positive margin (11.4% vs. 13.9% vs. 27.6% for T1, T2, and T3 tumors, respectively; P = 0.010). No difference was found in margin status after excision of palpable versus nonpalpable tumors (10.6% vs. 10.9%, respectively, P = 0.743). Histologic subtype, however, did affect margin status (15.8% vs. 9.8% positive margins for lobular vs. ductal type, respectively, P = 0.003). In this multi-institutional study, increasing tumor size and lobular histologic subtype were associated with a greater likelihood of a positive margin. The type of biopsy, needle or excisional, had no effect on the ability to achieve negative margins.