Determinants of Background Parenchymal Enhancement on breast MRI.

Background parenchymal enhancement (BPE) on breast magnetic resonance imaging (MRI) is a functional marker influenced by hormonal and vascular factors. It has been linked to breast cancer in prior studies, but shows wide variability across patient and clinical characteristics. Understanding its patterns is essential, yet data from Eastern European populations remain scarce. We retrospectively analyzed 353 women who underwent breast MRI at our center between January 2019 and January 2025. BPE and fibroglandular tissue (FGT) were classified according to Breast Imaging Reporting and Data System (BI-RADS). Patient age, menopausal status, body mass index (BMI), and tamoxifen use were recorded. Associations between BPE and clinical variables were evaluated with chi-square and Kruskal-Wallis tests. BPE decreased with age and was substantially lower in postmenopausal women (p<0.001). Women with heterogeneous (C) or extreme (D) FGT showed higher levels of BPE, reflecting the predominance of dense parenchyma among younger patients. BMI showed a modest but significant association (p=0.042), with overweight and obese women relatively more represented among moderate or marked enhancement. All patients on tamoxifen (n=25) displayed minimal BPE (p<0.001). In conclusion, BPE was strongly associated with age, menopausal status, FGT, and tamoxifen therapy in this cohort. These findings confirm its role as a hormonally driven imaging feature and underline the need to interpret BPE together with patient characteristics in daily practice.