Abstract:Objective To investigate the clinical characteristics and treatment options for simultaneous multiple primary cancers (MPC).Methods Using a case report of simultaneous MPC of the breast and rectum as an entry point, we reviewed the literature to summarize and analyze its clinical features and treatment programs.Results In this case, the development of simultaneous MPC of the breast and rectum may be the result of a combination of pathogenic factors.She underwent total mastectomy and radical rectal cancer surgery successively, and has been taking oral tamoxifen (TAM) as adjuvant therapy after the surgery. The patient has recovered well, and no abnormality has been found in the review, and she has the disease stable.Conclusion For simultaneous MPC of breast-rectal cancer, the efficacy of TAM for breast cancer is remarkable. Although in this case the disease was stable and progression-free after postoperative TAM treatment, the efficacy of TAM for rectal cancer needs to be further elucidated. In addition, early diagnosis and treatment are crucial for MPC patients, and individualized treatment plans need to be developed through a multidisciplinary diagnostic and treatment model.