ORIGINAL ARTICLE – BREAST ONCOLOGY Breast Conservation and Negative Margins in Invasive Lobular Carcinoma: The Impact of Oncoplastic Surgery and Shave Margins in 358 Patients Rita A. Mukhtar, MD 1 , Jasmine Wong, MD 1 , Merisa Piper, MD 2 , Zelos Zhu, BS 1 , Kelly Fahrner-Scott, BA 1 , Matina Mamounas, BS 1 , Hani Sbitany, MD 2 , Michael Alvarado, MD 1 , Robert Foster, MD 2 , Cheryl Ewing, MD 1 , and Laura Esserman, MD, MBA 1 1 Division of General Surgery, Department of Surgery, UCSF Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA; 2 Division of Plastic Surgery, Department of Surgery, University of California, San Francisco, San Francisco, CA ABSTRACT Background. Invasive lobular carcinoma (ILC) of the breast grows in a diffuse pattern, making complete surgical excision difficult. This results in high rates of positive margins and low rates of successful breast-conserving surgery. We hypothesized that utilizing oncoplastic surgi- cal techniques and selective shave margins would be associated with lower positive margin rates and increased breast conservation in women with ILC. Methods. We performed a retrospective cross-sectional analysis in a large cohort of prospectively collected ILC cases who received surgical treatment at the University of California, San Francisco, between 1992 and 2017. We identified all patients with histologically proven, unilateral or bilateral, stage 1–3 ILC. The primary outcome was positive margin rates, defined as no ink on tumor. Results. We identified 365 tumors in 358 women, with an average age of 61 years, who underwent breast-conserving surgery, and found that the use of oncoplastic techniques (odds ratio [OR] 0.4, 95% confidence interval [CI] 0.21–0.79, p = 0.008) and the selective use of shave mar- gins (OR 0.393, 95% CI 0.22–0.7, p = 0.002) were significantly associated with lower positive margin rates, when adjusted for tumor size and multifocality. The suc- cess rate for breast-conservation surgery was 75%, with a 25% conversion rate to mastectomy. Conclusions. Surgeons should consider routine use of oncoplastic techniques and shave margins when perform- ing breast-conservation surgery for women with ILC as these methods are associated with significantly lower odds of having positive margins and higher breast-conservation rates. Although breast-conservation surgery is a safe onco- logic procedure for breast cancer, the problem of incomplete excision, or positive margins, remains unre- solved. 1,2 Women who undergo breast-conservation surgery face a 10–60% chance of having a positive mar- gin. 3,4 This finding usually prompts a recommendation for a second operation since untreated positive margins are associated with a higher risk of cancer recurrence. 5 Whereas some women will have a re-excision to clear the margins, others will opt for mastectomy, lowering the success rate of attempted breast conservation. Many factors can influence the risk of positive margins, including tumor size relative to the breast, multifocality, and tumor histol- ogy. However, in no subtype is the problem of positive margins more prevalent than in invasive lobular carcinoma (ILC) of the breast. 4,6,7 ILC is the second most common type of breast cancer, and has unique challenges in its clinical management. 8–10 Characterized by the absence of the adhesion protein E-cadherin, ILC grows in a diffuse pattern, with histologic findings of ‘single files’ of tumors cells. This growth Electronic supplementary material The online version of this article (https://doi.org/10.1245/s10434-018-6682-4) contains supplementary material, which is available to authorized users. Ó Society of Surgical Oncology 2018 First Received: 16 April 2018 R. A. Mukhtar, MD e-mail: rita.mukhtar@ucsf.edu Ann Surg Oncol https://doi.org/10.1245/s10434-018-6682-4