ABSTRACT
Objective@#To investigate the relationship between breast cancer and thyroid cancer.@*Methods@#A cohort of 747 female patients with stage Ⅰ-Ⅲ invasive breast cancer were enrolled in this retrospective study. The differences of clinical and pathological data were compared between the simple breast cancer group (723 cases) and the breast cancer with thyroid cancer group (24 cases), to analyze the relevant factors of second primary thyroid cancer in patients with breast cancer.@*Results@#There were significant differences in the menstrual status and estrogen receptor (ER) status between the group of patients with breast cancer only and breast cancer patients with secondary primary thyroid cancer (P<0.05). Breast cancer patients with secondary primary thyroid cancer were more likely to be premenopausal (75%) and ER-positive (83.3%). Multivariate logistic regression analysis showed that the patient′s menstrual status (compared with premenopausal patients, peri-menopausal odds ratio=0.53, 95% CI 0.07-4.25; post-menopausal odds ration=0.23, 95%CI 0.08-0.65) and body mass index (BMI, odds ratio=1.14, 95%CI 1.02-1.28) were independent risk factors for secondary primary thyroid cancer in patients with breast cancer.@*Conclusion@#Thyroid cancer is associated with breast cancer, and is more likely to occur in obesity patients and premenopausal patients.