Based on morphologic and molecular findings, lesions that bridge between the resting endometrium and serous endometrial intraepithelial carcinoma (EIC) were designated as ‘Endometrial glandular dysplasia (EmGD)’ in 2004. EmGD may represent the earliest change in the development of endometrial serous carcinoma (ESC). Recently reported that about 20% of women with ESC had a history of breast cancer and the incidence was higher in patients who were at younger age. A 50-year-old woman who had an history of breast cancer and taking tamoxifen for several years was referred to clinic. Hysterectomy was performed. The microscopic examination showed an atrophic endometrium with endometrial glands and surface epithelium lined by atypical cells showing nucleomegaly, nuclear hyperchromasia, rare nucleoli, and no significant stratification. Rare papillae formation and atypical mitotic figures were present. p53 expression were evaluated by immunohistochemistry in these cells. EmGD can be diagnosed by routine microscopic evaluation and requires the careful exclusion of morphologic mimics, such as metaplastic processes and EICs. Characteristics of p53 and MIB-1 immunostains of EmGD may be of diagnostic usage in surgical pathology practice. Recognition of EmGD potentially offers the opportunity to prevent the development of the associated malignancy and may provide an opportunity to improve the management of uterine serous carcinoma.