Objective   To investigate the clinical characteristics and prognoses of breast cancer patients with other multiple primary cancers (MPCs).

  Methods   A total of 226 patients who underwent surgery for breast cancer and other MPCs at Tianjin Medical University Cancer Inseitute and Hospital between January 2005 and December 2015 were retrospectively selected. Clinical and pathological features and prognostic factors were investigated using univariate and multivariate analyses.

  Results   Of the 226 patients with breast cancer, 74 (32.7%) had synchronous cancers and 152 (67.3%) had metachronous cancers. Thyroid was the most prevalent cancer among the accompanying malignancies, affecting 90 patients. During a mean follow-up duration of 84.75 (4.13-84.5) months, the 3-year and 5-year overall survival rates of the 226 patients were 91.7% and 82.9%, respectively. Patients with MPCs showed a large tumor size (65.5% vs. 34.5%, P=0.005) and were positive for ER (76.1% vs. 23.9%, P=0.046) at the time of breast cancer diagnosis. The metachronous MPC group mainly comprised the elderly compared with the synchronous MPC group (62.4% vs. 37.6%, P < 0.001). MPC patients presenting with early lymph node stage (HR: 0.341-0.932, P=0.025) and metachronous cancers (HR: 0.033-0.220, P < 0.001) exhibited a better prognosis than the others.

  Conclusion   Thyroid cancer was the most frequently accompanying tumor. Patients with MPCs showed a large tumor size and were positive for ER. The metachronous MPC group demonstrated a preference for older people. Lymph node stage and style of MPCs are the independent factors for prognosis.