Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 58 4 2020 07 28 166 170 EN Elham Shobeiri Department of Radiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Mohsen Fath Ordoubadi Department of Radiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Marzieh Jahanian Department of Radiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Nasrin Amiri Department of Radiation Oncology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. 2019 10 17 2020 04 25 Estimation of breast tumor size is one of the most important diagnostic measures in determining the appropriate treatment. Mammography and ultrasound are the main methods for determining the size of breast tumors. The aim of this study was to compare the correlation between tumor size calculated by breast ultrasound and mammography with the results of pathologic measurements in malignant breast masses. Patients diagnosed with breast cancer by pathologic examination underwent mammography and ultrasound to determine the size of the tumor. The largest observed diameter in ultrasound and mammography was recorded as the tumor size. The mean (SD) tumor size measured by ultrasound (23.58±9.38 mm) was significantly less than the actual size based on histopathologic examination (28.87±11.17 mm) (P=0.008). However, there was no significant difference between the measurements performed between mammography (26.54±10.46 mm) and histopathology (P=0.18). The correlation coefficient between mammography and pathologic examination (r=0.61) was higher than the correlation coefficient between ultrasonography and pathology (r=0.5). Mammography, compared to breast ultrasound, had better accuracy in determining the size of malignant breast masses. https://acta.tums.ac.ir/index.php/acta/article/view/8137 https://acta.tums.ac.ir/index.php/acta/article/download/8137/5397