This study is a multicenter, open-label, randomized controlled trial. It will prospectively compare outcomes between patients undergoing reverse-sequence endoscopic NSM (R-E-NSM) with direct-to-implant breast reconstruction (DIBR) with the "HUAXI Hole 1" versus without the "HUAXI Hole 1". The study aims to evaluate differences in operative efficiency, surgical safety, postoperative aesthetics, and oncological safety between the two groups.

Conventional open nipple-sparing mastectomy (NSM) often results in significant surgical scarring, which is detrimental to the aesthetic outcome of the breast and the patient's psychosocial well-being. Meanwhile, endoscopic NSM has been reported to achieve favorable aesthetic outcomes and surgical safety. However, traditional endoscopic NSM has high technical difficulty and low surgical efficiency.

Our team has developed an innovative reverse-sequence endoscopic NSM (R-E-NSM) with direct-to-implant breast reconstruction (DIBR) following extensive research and clinical practice. This pioneering technique leverages the expansive force of gas to form a universal retractor. It employs an innovative reverse dissection sequence from deep to superficial layers, which retains the advantages of traditional endoscopic NSM while significantly improving operative efficiency. However, gland resection in the lower and inner quadrant of the breast remains technically challenging due to the long working distance and complex manipulation, often resulting in prolonged operative time and risks of incomplete gland resection.

To address these limitations, the West China Hospital team developed the "HUAXI Hole 1" technique-a 2-mm auxiliary incision at the superolateral edge of the areola, through which the electric scalpel is inserted to assist the gland resection. It can significantly reduce interference between instruments caused by the transaxillary single-incision approach and facilitate complete gland resection, which may contribute to improved surgical efficiency, surgical safety, and oncologic safety with the aesthetic advantages of the endoscopic technique. However, some researchers are concerned about the risks, such as nipple and areola complex (NAC) ischemia/necrosis, incision dehiscence, and surgical site infection. The prospective clinical evidence validating its efficacy and safety is currently lacking.

Therefore, this national multicenter, open-label, randomized controlled trial will prospectively compare outcomes between patients undergoing reverse-sequence endoscopic NSM (R-E-NSM) with direct-to-implant breast reconstruction (DIBR) with the "HUAXI Hole 1" versus without the "HUAXI Hole 1". The study aims to evaluate differences in operative efficiency, surgical safety, postoperative aesthetics, and oncological safety between the two groups.

Inclusion criteria:

• Female patients aged 18-70 years (inclusive18 and 70 years);
• Patients eligible for unilateral or bilateral reverse-sequence endoscopic nipple-sparing mastectomy with immediate implant-based breast reconstruction, with concurrent contralateral endoscopic augmentation mammoplasty permitted;
• Patients with preoperative pathological confirmation of non-specialized breast cancer (e.g., ductal carcinoma in situ, invasive ductal carcinoma, invasive lobular carcinoma) or eligibility for prophylactic mastectomy;
• For non-specialized breast cancer patients, preoperative tumor size ≤5 cm (post-neoadjuvant chemotherapy if applicable), and no clinical or imaging evidence of invasion to the nipple, skin, subcutaneous fat, chest wall (referring to the bony thorax and intercostal muscles, excluding the pectoralis major and minor muscles) or distant metastasis preoperatively;
• Patients volunteered to provide informed consent.

Exclusion criteria:

• History of open breast surgery within 1 year before this procedure (excluding minimally invasive vacuum-assisted biopsy);
• Breast cancer diagnosed during pregnancy or lactation;
• Subnipple-plane scarring with radiotherapy;
• Metastatic breast cancer (M1);
• Severe comorbidities precluding general anesthesia or surgery;
• BMI ≥40 kg/m²;
• HbA1c >7.5%;
• Immunodeficiency;
• Active smoking with ≥20 cigarettes per day
• Patients with concurrent participation in conflicting clinical trials.

Qualified researchers can request access to anonymized individual patient-level data via the request portal. All IPD requests should be emailed to Dr. Zhenggui Du, the general project leader, and will be evaluated by Dr. Du and the head of the collaborating organization to decide whether to approve.

After publication of relevant research outputs, such as academic papers and books.

When a request has been approved, the investigator will provide access to the de-identified individual patient-level data in the data management platform (Electronic Data Capture, EDC). A signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing the requested information. Additionally, all users will need to accept the terms and conditions of the data management platform to gain access.