Positive margins after mastectomy in patients with invasive lobular carcinoma of the breast: Incidence and management strategies.

Abstract Background Surgical treatment of invasive lobular carcinoma (ILC) is challenging due to its diffuse growth pattern, and the positive margin rate after mastectomy is poorly described. Methods We retrospectively determined the positive margin rate in those with stage I-III ILC undergoing mastectomy. We evaluated the relationship between management strategy and recurrence free survival (RFS). Results In 357 patients, the positive margin rate was 10.6% overall and 18.7% in those with T3 tumors. Having a positive margin was associated with significantly shorter RFS on multivariate analysis (p = 0.01). Undergoing additional local treatment (radiation or re-excision) for a positive margin was significantly associated with improved RFS (p = 0.004). Older women with positive margins were significantly less likely to undergo additional local therapy. Conclusions Even mastectomy fails to clear margins in a high proportion of patients with large ILC tumors, a finding which may warrant testing neoadjuvant strategies even prior to planned mastectomy.