Aim: To compare the survival outcomes between patients treated with bilateral mastectomy and partial mastectomy alone as the initial surgical management for primary lobular carcinoma in situ (LCIS). Patients and methods: Patients with histologically confirmed LCIS underwent partial mastectomy alone or bilateral mastectomy were identified by the SEER*Stat database (version 8.3.2) released in 2016. The primary outcome measure was all-cause mortality and the secondary outcome measure was breast cancer-specific mortality. Results: Of the 5964 cases included in the analysis, 208 cases underwent bilateral mastectomy and 5756 cases underwent partial mastectomy alone. The 1-, 5-and 10-year estimated overall survival rates were 99.7%, 96.7% and 91.7%, respectively. Univariate and multivariate proportional hazards regression (Cox) analyses showed no significant difference between the risk of all-cause mortality in the bilateral mastectomy group compared with the partial mastectomy group (HR = 1.106, 95% confidence interval [CI] 0.350-3.500, P = 0.86). In propensity score-matched model, bilateral mastectomy still did not show benefit to overall mortality (HR = 2.248, 95% CI 0.451-11.200). Patients older than 60 years of age showed a higher risk of all-cause mortality (HR = 7.593, 95% CI 5.357-10.764, P < 0.0001). No risk factors, including surgery type, were identified for breast cancer-specific survival. Conclusions: Survival outcomes of patients with LCIS who underwent partial mastectomy without radiotherapy were not inferior to patients who underwent bilateral prophylactic mastectomy. Breast cancer-specific mortality in patients with LCIS was extremely low; aggressive prophylactic surgery like bilateral prophylactic mastectomy should not be advocated for most patients with LCIS. (C) 2017 Elsevier Ltd. All rights reserved.