Objective: The aim of the present study was to determine the frequency and age-specific incidence rate of different histopathologic subtypes of breast cancer in Iran, and compare it to neighboring and Western countries and to discuss the probable effective main factors. Methods: National data from cancer registry for 6265 female breast cancer patients were studied in 10 histopathologic groups. Results: The most common tumor was ductal carcinoma (89%). The peak age – specific incidence rate of breast cancer in total, and for epithelial, non-epithelial and ductal carcinomas were all 50-59 years, and it decreased in older age. It is in contrast to US SEER report which shows the incidence increases in higher age. Conclusion: Three main factors including younger age of Iranian patients, probable more ERN tumors and different histopathological profile of breast cancer in Iran might be considered and studied to explain different slope of breast cancer after menopause compared to other countries.