Reproductive and Family-Structure Factors and Tumor Characteristics at Diagnosis in Iranian Women with Breast Cancer: A Retrospective Single-Center Study

Background Breast cancer is the most frequently diagnosed malignancy among women worldwide. Tumor characteristics at diagnosis vary considerably and may be shaped by biological, reproductive, and demographic factors. This study assessed whether reproductive and familial history are independently associated with tumor characteristics, with emphasis on proliferative activity at diagnosis. Methods We conducted a retrospective single-center study of 321 women diagnosed with breast cancer between 2017 and 2020 at Imam Hossein Hospital in Tehran, Iran. Tumor-related variables were abstracted from medical records, and reproductive and familial history variables were obtained from medical records when available and supplemented by structured telephone interviews when necessary. Associations between reproductive and familial factors and tumor characteristics (using Ki67 as the primary outcome) were evaluated using multivariable regression models appropriate to outcome type. Results Age was consistently associated with Ki67 and with prespecified secondary outcomes, including tumor grade, tumor size category, and metastatic disease at diagnosis. In adjusted analyses, each additional year of age was associated with an approximate 0.4 percentage-point decrease in Ki67, higher odds of metastatic disease at diagnosis, and lower odds of grade 3 tumors. No reproductive or familial history variables showed consistent independent associations with tumor characteristics after multivariable adjustment. Conclusion Age emerged as the primary factor related to tumor proliferative activity and selected tumor characteristics at diagnosis, whereas reproductive and familial history variables showed no independent associations after adjustment. Overall, the findings emphasize the importance of age-related influences in breast cancer presentation and support further investigation in larger populations to inform age-responsive risk assessment and early detection strategies.