The analysis of the histopathologic features in 138 patients with uterine serous adenocarcinoma in comparison with 146 patients with uterine endometrioid papillary adenocarcinoma revealed morphological specificities of these carcinomas. Immunohistochemical study found that 66.7% uterine serous adenocarcinomas were negative both to estrogen and progesterone receptors and 86.7% uterine serous adenocarcinomas showed p53 oncoprotein overexpression. The data support the hypothesis that uterine serous adenocarcinoma is a hormone-negative tumor and that mutation of p53 tumor suppressor gene may play a leading role in its carcinogenesis.