Aim: The study aimed to compare histopathological outcomes of the endometrium in breast cancer patients treated with tamoxifen. The analysis included asymptomatic women referred for abnormal ultrasound findings and symptomatic women with abnormal uterine bleeding. Materials and Methods: The study included 85 patients hospitalized between 2013 and 2024 at the Medical University of Warsaw. Group I (n=41) comprised patients with abnormal ultrasonographic findings, while Group II (n=44) included women with abnormal uterine bleeding. All patients underwent hysteroscopy with subsequent histopathological tissue analysis. Results: The most frequent histopathological diagnosis in both groups was the presence of endometrial polyps (Group I: 51.22%; Group II: 36.36%). Endometrial cancer was diagnosed in 7.32% of Group I and 9.09% of Group II patients, indicating a comparable prevalence of serious pathology. Statistically significan differences (p < 0.05) were noted between the groups only for non-atypical hyperplasia and proliferative endometrium. Conclusions: The findings confirm that endometrial polyps are the most frequent pathology associated with tamoxifen use in this cohort. This preliminary report underscores the critical need for further targeted research focusing on population-specific factors and menopausal status to develop clear, personalized clinical guidelines for screening and surveillance, particularly for premenopausal women, independent of symptomatic presentation.