BackgroundData on long-term cosmetic outcome, overall survival, and disease-free survival of endoscope-assisted partial mastectomy (EAPM) for breast cancer are scarce. Thus, we examined these outcomes after a 10-year follow-up period, and compared with conventional conservative method (CCM).Patients and methodsData on 257 patients with stage ≤ IIA breast cancer who underwent CCM (n = 125) or EAPM (n = 132) were analyzed. Cosmetic outcome at 2, 5, and 10 years was evaluated by 5 criteria (breast retraction assessment, nipple deviation, atrophy, skin change, scar). For overall mortality, breast cancer-specific mortality, and recurrence, the risk by operation method was tested by Cox proportional hazard models.ResultsEAPM performed significantly better than CCM in terms of cosmetic outcomes for location B at 2, 5, and 10 year-follow ups. As for cosmetic outcomes by individual criteria, EAPM had significantly higher proportions of satisfactory results for scar across all follow-up periods, and atrophy at 2-year and 10-year follow-up. There were no significant differences in terms of overall mortality, breast cancer-specific mortality, and recurrence between EAPM and CCM. The rates of patients who experienced local recurrence were similar between CCM and EAPM.ConclusionEAPM is better than CCM in terms of long-term cosmetic outcome, especially for location B. As a surgical treatment for breast cancer, EAPM is comparable to CCM in terms of mortality and recurrence.