ABSTRACT
BACKGROUND: The development mechanisms of Lynch syndrome (LS)-related breast cancer (BC) and rectal cancer are complex and variable, leading to personalized variations in diagnosis and treatment plans. CASE SUMMARY: This paper presents a comprehensive review of clinical diagnosis and treatment data from a patient with LS-associated BC and rectal cancer. Moreover, screening data and management guidelines, as well as relevant literature on LS, are included in this report. This study summarizes the molecular pathogenesis, clinicopathological features, and screening and management protocols for LS-associated BC and rectal cancer. CONCLUSION: Implementing early screening, prevention, and timely diagnosis and treatment measures is expected to reduce mitigate the incidence and mortality of LS-related BC and rectal cancer.