Bilateral Primary Breast Cancer: Current Evidence and Future Perspectives.

Bilateral primary breast cancer (BPBC) accounts for 2-12% of all breast cancers, with an increasing incidence trend. However, its clinical management remains challenged by the absence of unified diagnostic criteria, lack of evidence-based therapeutic guidelines, incomplete prognostic assessment frameworks, and a paucity of data from Asian populations. This narrative review critically synthesizes literature from PubMed, Web of Science, and CNKI databases (2020-2025) across seven dimensions: diagnosis and differential diagnosis, clinicopathological features, risk factors, imaging, genetics, treatment, and prognosis. Current evidence demonstrates that SBBC and MBBC exhibit significant heterogeneity in age at onset, molecular subtype distribution, and prognosis, with bilateral receptor discordance rates of 11-23%, mandating separate evaluation of each side; all current treatment recommendations are extrapolated from unilateral breast cancer evidence, leaving decisions in cases of subtype discordance without evidence-based support; and existing genetic risk models and clinical evidence are predominantly derived from Western populations, with only limited single-center retrospective data available from Asian populations but systematic, high-quality evidence remaining insufficient, such that direct application carries a risk of systematic bias. This review aims to provide an evidence-based reference for standardized clinical practice, emphasizing the urgent need to establish unified diagnostic criteria, develop population-specific risk models for Asian populations, and conduct dedicated prospective trials.