PURPOSE:Robot-assisted nipple-sparing mastectomy (RANSM) has gained acceptance in selected patients; however, identifying the safe dissection plane remains technically challenging due to the absence of tactile feedback. Artificial intelligence (AI)-guided navigation may provide intraoperative assistance, yet no externally validated model has been reported for this procedure. MATERIALS AND METHODS:This retrospective study developed and validated an AI-guided navigation system to identify the safe dissection plane during RANSM. Surgical video data from 37 procedures performed between January 2021 and December 2024 at two tertiary centers in South Korea were analyzed (internal dataset, n = 29; external dataset, n = 8). The safe dissection plane was annotated as the visual boundary between subcutaneous fat and glandular tissue. An AI segmentation model was trained using 5-fold cross-validation on the internal dataset and tested on the independent external dataset. Model performance was assessed using the Dice Similarity Coefficient (DSC), with intersection over union (IOU), sensitivity, precision, and specificity as secondary metrics. RESULTS:A total of 1996 internal and 293 external frames were analyzed. The model achieved a mean DSC of 74.0 % (±1.5 %), IOU: 60.0 % (±1.8 %), sensitivity: 79.7 % (±1.9 %), and precision: 71.5 % (±1.6 %) in internal validation. On external validation, the DSC was 70.8 %, IOU: 55.9 %, sensitivity: 73.1 %, precision: 72.2 %, and specificity: 96.8 %. CONCLUSION:This study is the first to develop and externally validate an AI-guided navigation system for RANSM. The model demonstrated consistent performance across two institutions, suggesting potential to enhance surgical precision and safety. Larger prospective studies are warranted to confirm clinical utility.

BACKGROUND:Nipple-sparing mastectomy (NSM) is a surgical option offering both oncological safety and cosmetic benefits. However, the oncological safety of NSM in carriers of BRCA1/2 pathogenic variants/likely pathogenic variants (PV/LPV) with breast cancer and the role of risk-reducing mastectomy remain underexplored, especially in Asian populations. This study evaluated the safety and effectiveness of NSM in BRCA1/2 PV/LPV carriers and assessed the preventive impact of contralateral risk-reducing NSM (RRNSM) on cancer incidence. METHODS:This multicentre retrospective study included women aged 20-80 years who underwent NSM for therapeutic or risk-reducing purposes and received germline BRCA1/2 tests between May 2006 and June 2022 across 19 institutions in Korea. Patients with distant metastasis at diagnosis were excluded. Information on demographics, the clinical characteristics of patients and tumours, surgical details, and follow-up outcomes was collected from a review the medical records of each participating institution. The primary outcome was the oncological safety of NSM, assessed by comparing ipsilateral local recurrence rates between patients with and without BRCA1/2 PV/LPV. The secondary outcome was cancer incidence in patients who underwent contralateral RRNSM versus those who did not. RESULTS:In all, 787 women underwent 906 NSMs, with a median (interquartile range) follow-up of 59.3 (44.0-82.8) months. Among the participants, 186 (23.6%) were BRCA1/2 PV/LPV carriers. Ipsilateral local recurrence rates were comparable between BRCA1/2 PV/LPV carriers and non-carriers (6.4 versus 7.4%, respectively). The 5-year local recurrence-free survival rates did not differ significantly between BRCA1/2 PV/LPV carriers and non-carriers (92.2% versus 93.2%, respectively; P = 0.87). Contralateral breast cancer occurred in 4.5% of patients with BRCA1/2 PV/LPV who did not undergo contralateral RRNSM, whereas no cases of contralateral breast cancer were reported among patients who underwent RRNSM regardless of BRCA1/2 status. CONCLUSIONS:This study highlights NSM as a safe and effective surgical option for BRCA1/2 PV/LPV carriers with breast cancer, as well as a risk-reducing strategy. Further prospective studies are needed to confirm these findings and evaluate long-term outcomes.

Background Pathologic complete response (pCR) after neoadjuvant chemotherapy (NACT) predicts favorable outcomes in HER2-positive and triple-negative breast cancer (TNBC). While breast and axillary pCR often coexist, some patients with residual breast disease still achieve axillary pCR. This study evaluated axillary pCR rates and factors in this subgroup, and the potential to omit sentinel lymph node biopsy (SLNB) in selected patients. Methods We retrospectively reviewed 1043 patients with HER2-positive or TNBC who did not achieve breast pCR after NACT and underwent surgery between 2008 and 2021 at a single institution. Clinicopathological features were compared between axillary pCR and non-pCR groups. Logistic regression analyses identified predictors of axillary pCR. Results Axillary pCR was observed in 648 (62.1 %) of 1043 patients who did not achieve breast pCR after NACT. The axillary pCR rate was 91.3 % in clinically node-negative (cN0) patients and 55.4 % in cN-positive patients. Axillary pCR rates decreased as the size of the residual breast tumor increased in both cN0 and cN-positive patients. Axillary pCR rates exceeded 94 % in patients with cN0 and residual tumor size of 1 cm or less. Multivariable analysis identified lower clinical N stage, smaller residual breast tumor size, and absence of lymphovascular invasion as independent predictors of axillary pCR. Conclusions A substantial proportion of HER2-positive or TNBC patients without breast pCR after NACT achieved axillary pCR, especially those with cN0 status and small residual tumors. These results support the potential omission of SLNB in selected patients and highlight the need for prospective validation and predictive model development.

Robot-assisted breast-conserving surgery has a potentially better cosmetic benefit than conventional breast-conserving surgery without any scarring on the breast. However, data on the feasibility and safety are limited. This study presents the results of early robot-assisted breast-conserving surgery. A multi-center retrospective review was conducted to identify women who underwent robot-assisted breast- conserving surgery between August 2019 and October 2023. Information on the clinicopathological characteristics, perioperative complications, operation time, recurrence, and reoperation was collected. A total of 150 patients underwent the surgery performed by ten breast surgeons at seven institutions. Invasive breast cancer was observed in 121 cases and ductal carcinoma in situ was detected in 29 cases. Of all the patients, 75.3

BACKGROUND:Robot-assisted nipple-sparing mastectomy (RANSM) has transformed breast cancer surgery by offering precise dissection, reduced scarring, and quicker recovery. Single-port RANSM (SP-RANSM) builds on these advancements, with debates surrounding the use of tumescent dissection technique owing to potential complications and increased operative time. This study compares the early postoperative outcomes of the two techniques to guide surgical decision-making and improve patient care. PATIENTS AND METHODS:We analyzed data from patients who underwent SP-RANSM between January 2018 and November 2023 across 12 South Korean institutions. The analysis focused on operative times, surgical details, and adverse events, comparing the tumescent-free and tumescent techniques. RESULTS:The cohort included 280 patients who underwent tumescent-free SP-RANSM and 150 who underwent tumescent SP-RANSM. The tumescent group had a greater prevalence of comorbidities, fewer multifocal but more multicentric lesions, and more tissue expander reconstruction. A total of 179 patients, representing 39.8%, were clinically staged at stage II or above. The tumescent-free group had longer predocking times but shorter console times and less intraoperative bleeding. Total operative times were similar between the two techniques. Adverse events occurred in 16.8% of tumescent-free and 23.3% of tumescent patients, with no significant difference in the distribution of adverse event types between groups. The most common adverse events were seroma and bleeding/hematoma. CONCLUSIONS:Both tumescent-free and tumescent SP-RANSM can be safely implemented with appropriate patient selection and surgical expertise. Future research should focus on long-term outcomes, cost-effectiveness, and patient-reported outcomes to further guide clinical practice in robotic breast surgery.

ImportanceWhile nipple-sparing mastectomy (NSM) for breast cancer was only performed using the open method in the past, its frequency using endoscopic and robotic surgical instruments has been increasing rapidly. However, there are limited studies regarding postoperative complications and the benefits and drawbacks of minimal access NSM (M-NSM) compared with conventional NSM (C-NSM).ObjectiveTo examine the differences in postoperative complications between C-NSM and M-NSM.Design, Setting, ParticipantsThis was a retrospective multicenter cohort study enrolling 1583 female patients aged 19 years and older with breast cancer who underwent NSM at 21 university hospitals in Korea between January 2018 and December 2020. Those with mastectomy without preserving the nipple-areolar complex (NAC), clinical or pathological malignancy in the NAC, inflammatory breast cancer, breast cancer infiltrating the chest wall or skin, metastatic breast cancer, or insufficient medical records were excluded. Data were analyzed from November 2021 to March 2024.ExposuresM-NSM or C-NSM.Main Outcomes and MeasuresClinicopathological factors and postoperative complications within 3 months of surgery were assessed. Statistical analyses, including logistic regression, were used to identify the factors associated with complications.ResultsThere were 1356 individuals (mean [SD] age, 45.47 [8.56] years) undergoing C-NSM and 227 (mean [SD] age, 45.41 [7.99] years) undergoing M-NSM (35 endoscopy assisted and 192 robot assisted). There was no significant difference between the 2 groups regarding short- and long-term postoperative complications (<30 days: C-NSM, 465 of 1356 [34.29%] vs M-NSM, 73 of 227 [32.16%]; P = .53; <90 days: C-NSM, 525 of 1356 [38.72%] vs M-NSM, 73 of 227 [32.16%]; P = .06). Nipple-areolar complex necrosis was more common in the long term after C-NSM than M-NSM (C-NSM, 91 of 1356 [6.71%] vs M-NSM, 5 of 227 [2.20%]; P = .04). Wound infection occurred more frequently after M-NSM (C-NSM, 58 of 1356 [4.28%] vs M-NSM, 18 of 227 [7.93%]; P = .03). Postoperative seroma occurred more frequently after C-NSM (C-NSM, 193 of 1356 [14.23%] vs M-NSM, 21 of 227 [9.25%]; P = .04). Mild or severe breast ptosis was a significant risk factor for nipple or areolar necrosis (odds ratio [OR], 4.75; 95% CI, 1.66-13.60; P = .004 and OR, 8.78; 95% CI, 1.88-41.02; P = .006, respectively). Conversely, use of a midaxillary, anterior axillary, or axillary incision was associated with a lower risk of necrosis (OR for other incisions, 32.72; 95% CI, 2.11-508.36; P = .01). Necrosis occurred significantly less often in direct-to-implant breast reconstruction compared to other breast reconstructions (OR, 2.85; 95% CI, 1.11-7.34; P = .03).Conclusions and RelevanceThe similar complication rates between C-NSM and M-NSM demonstrates that both methods were equally safe, allowing the choice to be guided by patient preferences and specific needs.

Abstract Purpose: Nipple-sparing mastectomy (NSM) is known for its excellent cosmetic results and acceptable oncologic safety. However, evidence supporting NSM in breast cancer (BC) patients carrying pathogenic variant (PV) or likely pathogenic variant (LPV) in BRCA1/2 genes is still limited. This study aims to evaluate the oncologic safety of NSM in BC patients and examine its preventive effect in unaffected individuals with BRCA1/2 PV/LPV. Methods: In this multicenter, retrospective study was conducted by the Korea Robot-Endoscopic minimal access Breast Surgery study Group (KoREa-BSG). We evaluated data from women who underwent NSM and BRCA1/2 genetic testing across 19 South Korean institutions. This study included BC patients aged between 20 and 80 years who had NSM and BRCA1/2 genetic testing between January 2008 and December 2018. Patients with distant metastasis at the initial diagnosis were excluded. Results: A total of 786 women, encompassing 906 NSM cases, were included. This population comprised 120 patients who underwent bilateral NSM, 666 with unilateral NSM for unilateral BC. Among them, 214 who received neoadjuvant chemotherapy. The median follow-up period was 62 months, with an age range of 26-74 years (median 44). Sentinel lymph node biopsy was carried out in 74.7% of cases. In the bilateral NSM cohort (n=120), 36 were bilateral BC patients, 41 were unaffected carriers of BRCA1/2 PV/LPV who underwent bilateral risk-reducing NSM (RRNSM), and 33 presented with unilateral BC with BRCA1/2 PV/LPV. In the subset of 33 patients who underwent contralateral RRNSM for unilateral BC, incidental ductal carcinoma in situ (DCIS) was discovered in two cases. In comparing NSM outcomes according to BRCA status, we found no significant difference in local recurrence (LR) between BC patients with BRCA1/2 PV/LPV (n=172) and those without BRCA1/2 PV/LPV (n=592) (LR rates: 11 in BRCA1/2 PV/LPV vs. 45 in non-carriers; p = 0.7965). Of the 172 BRCA1/2 PV/LPV carriers who did not undergo RRNSM, contralateral BC occurred in 11 patients (6.4%), while no recurrence was recorded in the RRNSM group. Conclusions: NSM appears to be a feasible option in BC patients with BRCA1/2 PV/LPV. While the long-term impact of NSM on breast cancer prevention in BRCA1/2 PV/LPV carriers requires further investigation, current evidence suggests that NSM could serve as an effective risk-reducing strategy. Citation Format: Hong-Kyu Kim, Sung Yoon Jang, Soong June Bae, Eun Young Kim, Chihwan Cha, Hyung Seok Park, Jeeyeon Lee, Jun-Hee Lee, Eun-Shin Lee, Jung Eun Choi, Soo Youn Bae, Hee-Chul Shin, Dongwon Kim, Moo Hyun Lee, Yong-Yeup Kim, Sang-Ah Han, Janghee Lee, Youngwoo Chang, Junwon Min, Sanghwa Kim, Hee Jun Choi, Young-Joon Kang, Sae Byul Lee, Jai Min Ryu. Oncologic Safety and Preventive Impact of Nipple-Sparing Mastectomy in BRCA1/2 Mutation Carriers: A Multicenter Retrospective Study of the Korea Robot-Endoscopy Minimal Access Breast Surgery Study Group (KoREa-BSG) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-08-12.

A 2 mm resection margin is considered adequate for ductal carcinoma in situ (DCIS). We assessed the effectiveness of a tailored radiation dose for margins < 2 mm and the appropriate margin width for high-risk DCIS. We retrospectively evaluated 137 patients who received adjuvant radiotherapy after breast-conserving surgery for DCIS between 2013 and 2019. The patients were divided into three– positive, close (< 2 mm), and negative (≥ 2 mm) margin groups. Radiation dose to the tumor bed in equivalent dose in 2 Gy fractions were a median of 66.25 Gy, 61.81 Gy, and 59.75 Gy for positive, close, and negative margin groups, respectively. During a median follow-up of 58 months, the crude rates of local recurrence were 15.0%, 6.7%, and 4.6% in the positive, close, and negative margin groups, respectively. The positive margin group had a significantly lower 5-year local recurrence-free survival (LRFS) rate compared to the close and negative margin groups in propensity-weighted log-rank analysis (84.82%, 93.27%, and 93.20%, respectively; p = 0.008). The difference in 5-year LRFS between patients with the high- and non-high-grade tumors decreased as the margin width increased (80.4% vs. 100.0% for margin ≥ 2 mm, p < 0.001; 92.3% vs. 100.0% for margin ≥ 6 mm, p = 0.123). With the radiation dose tailored for margin widths, positive margins were associated with poorer local control than negative margins, whereas close margins were not. Widely clear margins (≥ 2 mm) were related to favorable local control for high-grade DCIS.

543 Background: Robot-assisted breast conserving surgery (RABCS) have cosmetic benefit without any scar on the breast over conventional breast conserving surgery (CBCS). However, data on the feasibility and safety of the RABCS are limited. The aim of this study was to present the results of early experience of RABCS. Methods: A multi-center retrospective review was conducted to identify women who underwent RABCS as part of the Korea Robot-Endoscopy & Minimal Access Breast Surgery Study Group (KoREa-BSG) between August 2019 and October 2023. Information of the clinicopathologic characteristics, perioperative complications, operation time, recurrence, and re-operation were collected. Results: A total of150 patients underwent the RABCS procedure conducted by 10 breast surgeons at seven institutions. Invasive breast cancer was noted in 121 cases and ductal carcinoma in-situ was detected in 29 cases. Further, 75.3% and 65.3% of the patients had an estrogen and progesterone receptor positive status, respectively. A total of 35.3% of the patients had a HER2-positive status. In terms of the surgical technique, the Da Vinci SP system was more frequently used (60%). Gas insufflation was applied in 97.33% of the cases, and s entinel lymph node biopsy (SLNB) only was the most common axillary surgery (89.3%). The median duration of postoperative days was 5.4 days (range, 1.0-15.0 days). The incision location was the mid-axillary line and the median incision length was 37.1 mm (range, 27.0-60.0 mm). The median total operation time was 133.8 minutes (range, 62.0-295.0 minutes). 11 cases (7.3%) showed frozen margin positive, however only one case (0.7%) required re-operation because of permanent margin positive. Six patients (4%) developed surgical complications. Postoperative bleeding was found in one case and skin burn was found in five cases (3.3%); two cases (1.3%) required skin excision and three cases (2.0%) showed spontaneous resolution. There were no cases of conversion to open surgery or mortality. Only one case (0.7%) had recurrence. Conclusions: This was the first multicenter report of RABCS in the world. RABCS could be a technically feasible and safe. Further subsequent comparative study with CBCS and prospective research are needed to evaluate the surgical and oncologic outcomes.

PurposeThe incidence of early tumor detection is increasing due to popularization of breast cancer screening and the development of imaging techniques. Thus, suitable preoperative localization is required for proper diagnosis and treatment of non-palpable breast lesions. The purpose of this study was to evaluate the efficacy and safety of indocyanine green (ICG)-hyaluronic acid (HA) mixture for lesion localization compared to activated charcoal.MethodsThis was a multicenter, randomized, open-label, parallel phase 3 clinical trial performed at four centers in Korea. Female patients scheduled for surgery to remove non-palpable breast lesions were enrolled. One hundred and nine patients were randomly assigned to a control group (activated charcoal: 0.3. – 1 mL) or a study group (ICG-HA mixture, 0.2 mL) for the localization of a breast lesion. The primary endpoint was the accuracy of resection. Secondary endpoints included the technical success rate, histopathological accuracy, skin pigmentation rate, and adverse event rate.ResultsA total of 104 patients were eligible for per-protocol analysis (control group, n = 51; study group, n = 53). The accuracy of resection in the study group was not inferior to that of the control group (90.57% vs. 98.04%, 95% confidence interval (CI): -2.31 – 18.91, p = 0.21). There was no statistically significant difference in technical success rate between the two groups (marking on breast skin: p = 0.11, marking on the excised specimen: p = 0.12). However, there were statistically significant differences in histopathological accuracy (0.26 ± 0.13 vs. 0.33 ± 0.17, p = 0.01) and skin pigmentation rate (0.00% vs. 30.77%, p< 0.01). Adverse events were not reported in either group.ConclusionsWhen localization was performed using ICG-HA, the accuracy of resection was not inferior to that of activated charcoal. However, skin pigmentation rate was significantly lower. In conclusion, ICG-HA is effective and safe for localizing of non-palpable breast lesions.

PURPOSE:Positive margins after breast-conserving surgery are associated with poor oncological outcomes and warrant additional surgery. This study aimed to evaluate the effectiveness of high-dose radiation therapy for positive margins by comparing local recurrence between patients with positive and negative margins. METHODS:We retrospectively evaluated 550 patients treated with adjuvant radiation therapy after breast-conserving surgery for invasive breast cancer between 2013 and 2019. The total equivalent dose in 2 Gy fractions (EQD2) to the tumor bed ranged from 65.81 to 66.25 Gy for positive margins and 59.31-61.81 Gy for negative margins. The differences in local recurrence between the positive and negative margin groups were analyzed. RESULTS:After a median follow-up of 58 months, the crude local recurrence rate was 7.3% in the positive margin group (n = 55) and 2.4% in the negative margin group (n = 495). Positive margins were associated with higher local recurrence without statistical significance in the entire cohort (p = 0.062). Among patients aged <60 years, those with positive margins had a significantly lower 5-year local recurrence-free survival rate than those with negative margins (89.16% vs. 97.57%, respectively; p = 0.005). In contrast, there was no significant difference in the 5-year local recurrence-free survival rate between patients with positive and negative margins among those aged ≥60 years (100.00% vs. 94.38%, respectively; p = 0.426). CONCLUSION:In this study, positive margins were not associated with poor local control in older patients after a high-dose boosts. Further prospective studies are needed to verify our findings.

BACKGROUND:Breast cancer in young women has been shown to have an aggressive behavior and poor prognosis. AIM:To evaluate the outcomes of young hormone receptor (HR)-positive patients with breast cancer treated with neoadjuvant chemotherapy (NAC), and the oncologic efficacy of gonadotropin-releasing hormone (GnRH) agonists. METHODS:This retrospective study involved a prospectively enrolled cohort. We included patients diagnosed with invasive breast cancer who were treated with NAC followed by curative surgery at the Samsung Medical Center and Samsung Changwon Hospital between January 2006 and December 2017. Among patients with HR-positive and human epidermal grow factor 2 (HER2)-negative breast cancer, we analyzed the characteristics and oncology outcomes between the patients equal to or younger than 35 years and the patients older than 35 years. RESULTS:Among 431 patients with NAC and HR-positive/HER2-negative breast cancer, 78 were 35 years old or younger, and 353 patients were older than 35 years. The median follow-up was 71.0 months. There was no statistically significant difference in disease free survival (DFS, P = 0.565) and overall survival (P = 0.820) between the patients equal to or younger than 35 years and the patients older than 35 years. The two groups differed in that the GnRH agonist was used more frequently in the group of patients equal to or younger than 35 years than in the other group (52.4% vs 11.2%, P < 0.001). Interestingly, for the DFS according to the GnRH agonist in the group of patients equal to or younger than 35 years, patients treated with the GnRH agonist had better DFS (P = 0.037). CONCLUSION:Administration of GnRH agonists might improve the DFS rate of HR-positive/HER2-negative breast cancer in the equal to or younger than 35 years group of patients with NAC.

This study compared the surgical outcomes of transoral endoscopic thyroidectomy vestibular approach (TOETVA) and transoral robotic thyroidectomy (TORT) in papillary thyroid cancer (PTC).

PURPOSE:We evaluated the relationship between breast pathologic complete response (BpCR) and axillary pathologic complete response (ApCR) after neoadjuvant chemotherapy (NACT) according to nodal burden at presentation. As the indications for NACT have expanded, clinicians have started clinical trials for the omission of surgery from the treatment plan in patients with excellent responses to NACT. However, the appropriate indications for axillary surgery omission after excellent NACT response remain unclear.METHODS:Data were collected from patients in the Korean Breast Cancer Society Registry who underwent NACT followed by surgery between 2010 and 2020. We analyzed pathologic axillary nodal positivity after NACT according to BpCR stratified by tumor subtype in patients with cT1-3/N0-2 disease at diagnosis.RESULTS:A total of 6,597 patients were identified. Regarding cT stage, 528 (9.5%), 3,778 (67.8%), and 1,268 (22.7%) patients had cT1, cT2, and cT3 disease, respectively. Regarding cN stage, 1,539 (27.7%), 2,976 (53.6%), and 1,036 (18.7%) patients had cN0, cN1, and cN2 disease, respectively. BpCR occurred in 21.6% (n = 1,427) of patients, while ApCR and pathologic complete response (ypCR) occurred in 59.7% (n = 3,929) and ypCR 19.4% (n = 1,285) of patients, respectively. The distribution of biologic subtypes included 2,329 (39.3%) patients with hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative disease, 1,122 (18.9%) with HR-positive/HER2-positive disease, 405 (6.8%) with HR-negative/HER2-positive disease, and 2,072 (35.0%) with triple-negative breast cancer . Among the patients with BpCR, 89.6% (1,122/1,252) had ApCR. Of those with cN0 disease, most (99.0%, 301/304) showed ApCR. Among patients with cN1-2 disease, 86.6% (821/948) had ApCR.CONCLUSION:BpCR was highly correlated with ApCR after NACT. In patients with cN0 and BpCR, the risk of missing axillary nodal metastasis was low after NACT. Further research on axillary surgery omission in patients with cN0 disease is needed.

Objective: The aim of this study was to present the results of early experience of robot-assisted nipple sparing mastectomy (RANSM). Background: RANSM improves cosmetic outcomes over conventional nipple-sparing mastectomy. However, data on the feasibility and safety of the RANSM are limited. Methods: Patients who underwent RANSM with immediate breast reconstruction as part of the Korea Robot-endoscopy Minimal Access Breast Surgery Study Group (KoREa-BSG) from November 2016 to January 2020 were enrolled. clinicopathologic characteristics, perioperative complications, and operation time were collected. Results: Overall, 73 women underwent 82 RANSM procedures conducted by 11 breast surgeons at 8 institutions. The median patient age was 45.5 years old (20-66 years), and 52 (63.4%) patients were premenopausal. Invasive breast cancer was noted in 55 cases (40 cases were stage i, 11 cases were stage ii, and 4 cases were stage iii, respectively) and ductal carcinoma in-situ was recorded in 20 cases. Of those, 3 patients with BRCA1/2 mutation carriers underwent contralateral risk-reducing RANSM. The median length of hospitalization was 12.0 days (5.0-24.0 days). The incision location was the mid-axillary line and the median incision length was 50.0 mm (30.0-60.0 mm). Median total operation time, median total mastectomy time, and median reconstruction time was 307.0 minutes (163.0-796.0 minutes), 189.5 minutes (97.5-325.0 minutes), and 119.5 minutes (45.0-689.0 minutes). Only 2 cases (2.5%) required reoperation. Nipple ischemia was found in 9 cases (10.9%) but only 1 case (1.2%) required nipple excision given that 8 cases (9.7%) resolved spontaneously. Skin ischemia was observed in 5 cases (6.1%) and only 2 (2.4%) cases needed skin excision whereas 3 cases (3.6%) resolved spontaneously. There was no conversion to open surgery orcases of mortality. The mean time for mastectomy among surgeons who performed more than 10 cases was 182.3 minutes (+/- 53.7, minutes) and 195.4 minutes (+/- 50.4, minutes). Conclusion: This was the first report of RANSM conducted in the KoREa-BSG. RANSM is technically feasible and acceptable with a short learning curve. Further prospective research to evaluate surgical and oncologic outcomes is needed.