Abstract Background: The anatomic boundaries of conventional nipple-sparing mastectomy (NSM) is poorly defined. As such, deeper support structures, such as the circummammary ligament, the anterior lamellar fascia, and adjacent perforators, lymphatics and nerves are disrupted, compromising perfusion, wound healing, and reconstructive outcomes. The structural mastectomy preserves these structures to enhance perfusion, reduce complications, and facilitate direct-to-implant (DTI) reconstruction without acellular dermal matrices in the prepectoral plane. This study evaluates reconstructive outcomes associated with structural versus conventional NSM with immediate DTI reconstruction. Methods: A retrospective review was conducted of all patients who underwent NSM with DTI reconstruction at a single institution between November 2020 and July 2024. Patients were stratified by mastectomy technique into those who received a structural NSM (s-NSM) and those who underwent conventional non-structural NSM. s-NSM was characterized by the preservation of the circummammary ligament, superficial fascial system, and associated neurovascular bundles through dissection along well-visualized planes through a 6 cm incision. Primary outcome was short-term (≤30 days) and long-term (30 days) reconstructive complications. Results: A total of 122 patients (225 breasts) underwent conventional NSM (135 breasts, 60.0%) or s-NSM (90 breasts, 40.0%) with immediate DTI reconstruction. Baseline demographics, comorbidity profiles, and oncologic indications were similar between groups. Compared with conventional NSM, s-NSM was associated with shorter operative time (p=0.002), lower ADM use (55.6% vs. 94.1%, p0.001), and greater rates of NAC reinnervation (70.0% vs. 26.7%, p0.001). Oncologic outcomes were equivalent between groups. Short-term complications occurred less frequently following s-NSM (5.6% vs. 20.0%, p=0.003), including a significantly lower rate of partial nipple-areola complex necrosis (1.1% vs. 8.2%, p=0.030). On multivariate analysis, s-NSM remained independently protective against short-term reconstructive complications (OR 0.09, 95% CI 0.02-0.50, p=0.006), with good model discrimination confirmed by an area under the curve value (AUC) of 0.80. Long-term complication rates were also significantly less common following s-NSM (2.2% vs. 11.1%, p=0.018), though this did not remain statistically significant on multivariate analysis. The s-NSM was also associated with a significantly lower incidence of capsular contracture (2.2% vs. 11.1%, p=0.018). While fewer patients in the s-NSM cohort underwent elective aesthetic revision (11.1% vs. 20.0%, p=0.078), this did not reach statistical significance. Rates of positive margins (NSM: 3.7% vs. s-NSM: 3.6%, p=1.000), local recurrence (3.0% vs. 0.0%, p=0.529), distant metastasis (6.1% vs. 0.0%, p=0.117), and cancer-related death (5.3% vs. 0.0%, p=0.107) did not differ significantly. No differences in the instance of residual disease, tumor size, nodal metastasis, extranodal extension, or pathologic staging was observed between groups upon evaluation of final tumor pathology. Conclusion: For the first time, we demonstrate that structural preservation in breast surgery allows for efficacious single-stage reconstruction, limits ADM use, and improves reconstructive complication profiles early 1-year follow-up. While oncologic outcomes were not the primary focus of this study, overall survival and local recurrence rates were similar to those reported in prior series. The structural NSM may represent a paradigm shift in oncoplastic breast surgery in appropriately selected patients contributing to more favorable reconstructive outcomes. Citation Format: L. De La Cruz, R. N. Rohrich, A. Junn, M. E. Currin, D. H. Song, K. L. Fan. The Structural Mastectomy: Application of circum-mammary ligament preservation in nipple-sparing mastectomy abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-01-09.
Cruz et al. (Tue,) studied this question.