ObjectiveTo investigate the effectiveness of axillary single-site laparoscopic subcutaneous mastectomy in treatment of gynecomastia (GYN) and the assessment method of glandular mass before operation. Methods A clinical data of 65 GYN patients admitted between August 2023 and February 2024 and matched the selection criteria was retrospectively analyzed. The patients were (30.8±7.9) years old, with a body mass index (BMI) of 27.3 (24.9, 29.8) kg/m2. According to Simon’s grading criteria, the GYN was classified as gade Ⅰ in 8 cases, grade Ⅱa in 32 cases, grade Ⅱb in 21 cases, and grade Ⅲ in 4 cases. All patients underwent bilateral axillary single-site laparoscopic subcutaneous mastectomy. The operation time, intraoperative blood loss, postoperative bilateral extubation time, total length of hospital stay, and the occurrence of related complications were recorded. The cosmetic outcome score was assessed by questionnaire at 2 months after operation. Preoperative BMI, lying/standing sternal notch to nipple (SN-N), and lying/standing nipple to nipple (N-N) were measured. The differences in SN-N between standing and lying positions (ΔSN-N) and in N-N between lying and standing positions (ΔN-N) were calculated. The intraoperative resected glandular mass was recorded. The glandular mass-related indicators (BMI, ΔSN-N, ΔN-N) were compared between Simon grades. Spearman’s correlation analysis and multiple linear regression analysis of glandular mass with BMI and ΔSN-N, ΔN-N and Simon grading (grades Ⅰ, Ⅱa, Ⅱb, and Ⅲ were assigned values of 1, 2, 3, and 4, respectively) of the corresponding side. ResultsAll operations were successfully completed with the operation time of 75.0 (60.0, 90.0) minutes, the intraoperative blood loss of 12.0 (11.0, 13.0) mL, and the bilateral extubation time of 1.5 (1.5, 1.5) days after operation. The total length of hospital stay was 3.0 (3.0, 3.0) days. Three cases of subcutaneous hematoma in the chest wall and 1 case of nipple areola numbness and discomfort occurred after operation, while the rest of the patients had no complication, such as postoperative haemorrhage, effusion, infection, and nipple areola necrosis. The subjective cosmetic scores were all 15 at 2 months after operation, which was very satisfactory. The differences in ΔSN-N of right side between Simon grade Ⅰ and grades Ⅱa, Ⅱb, Ⅲ and in ΔSN-N of left side between Simon grade Ⅰ and grades Ⅱb, Ⅲ were significant (P<0.05), while the differences between the remaining grades were not significant (P>0.05). The differences in ΔN-N between Simon grade Ⅱa and gradeⅡb and in BMI between Simon grade Ⅱb and grade Ⅲ were not significant (P>0.05), while the differences between the remaining grades were significant (P<0.05). The glandular masses of left and right breasts in 65 patients were 69.0 (52.1, 104.0) g and 73.0 (56.0, 94.0) g, respectively; and the difference between left and right breasts was not significant (Z=−0.622, P=0.534). The data of the right breast was selected for correlation analysis. Correlation analysis showed that the right glandular mass was positive correlated with BMI and Simon grading, ΔSN-N, and ΔN-N (P<0.05). Multiple linear regression analysis showed that Simon grading had a positive predictive effect on glandular mass, and the regression equation was as follows: right glandular mass=5.541+32.115×Simon grading (R2=0.354, P<0.001). ConclusionAxillary single-site laparoscopic subcutaneous mastectomy is an ideal surgical procedure for the treatment of GYN. BMI and Simon grading are closely related to GYN glandular mass, and have certain reference value for preoperative glandular mass assessment.