Nipple-Sparing Mastectomy and Adequate Margins for Patients With Ductal Carcinoma In Situ

Background For patients with ductal carcinoma in situ (DCIS) undergoing breast conservation surgery (BCS), guidelines advise a margin width of at least 2 mm, with studies demonstrating decreased recurrence risk compared to narrower margins. However, limited data exist establishing if this margin is appropriate in mastectomies, and specifically for nipple-sparing mastectomy (NSM). Consequently, we evaluated the margins of DCIS patients undergoing NSM and resulting oncologic outcomes. Methods A single-institution retrospective review was performed in patients with DCIS or DCIS with microinvasion (DCIS + MI) undergoing NSM from April 2010 to December 2021. Patient and tumor characteristics, margin status, treatment, and outcomes information were collected. The association between margins and local-regional (LRR) and distant recurrence (DR) were examined. Results 161 patients were included, comprising 284 NSM (164 therapeutic, 120 prophylactic). 153 patients had DCIS and 8 had DCIS + MI. Most patients had hormone sensitive, 123 (76.4%), and nuclear grade 2, 72 (44.7%), disease. In total, 35 (21.7%) patients had positive or <2 mm margins. Of these, 21 (60%) involved the anterior margin. At a median follow-up of 45 months (range 0-151), 2.5% (n = 4) had a LRR and .6% (n = 1) had a DR. Of patients with a recurrence, only 2 had positive or <2 mm margins, 1 had received endocrine therapy, and none received adjuvant radiation. Discussion No specific margin status was found to correlate with recurrence for patients with DCIS or DCIS + MI undergoing NSM, with an altogether low recurrence risk. Overall, this suggests that recommended DCIS margins in BCS doesn’t necessarily apply in NSM, where margins of <2 mm may be acceptable.