AbstractThe majority of endometrial cancers are relatively benign and curable; there is a subset of virulent tumors that demands recognition. Factors that must be evaluated include: tumor grade, ploidy, steroid receptors, myometrial invasion, lymph node status, extrauterine disease or positive peritoneal fluid, and certain special tumors. These tumors of special virulence include: papillary adenocarcinoma, papillary serous adenocarcinoma, adenosquamous carcinoma, and clear cell carcinoma. Virulent tumors (approximately 20%) require special consideration and special treatment.