A 54-year-old woman with menorrhagia

The principal differential considerations for papillary carcinomatous proliferations of the endometrium have traditionally been uterine papillary serous carcinoma and villoglandular adenocarcinoma. Recently, another variant of endometrioid carcinoma that may also show papillary structures was described and designated endometrioid carcinoma with small nonvillous papillae (SNVP). In contrast to the papillary structures of uterine papillary serous carcinoma, the SNVP have cells that lack a high nuclear-to-cytoplasmic ratio and typically show exuberant eosinophilic cytoplasm. Additionally, the other typical morphologic patterns of uterine papillary serous carcinoma, such as slitlike spaces, highly pleomorphic nuclei, small detached cell clusters, and psammoma bodies, are absent. Overall, the clinicopathologic characteristics of this tumor are more consistent with endometrioid carcinoma and as such should be clearly distinguished from uterine papillary serous carcinoma. Herein, we report an example of a mixed mucinous and endometrioid carcinoma with prominent SNVP in both components.