Papanicolaou, George Nicholas (1883–1962), American anatomist and cytologist. Papanicolaou devoted his medical research almost entirely to the physiology of reproduction and exfoliative cytology. In 1917 he began studying the vaginal discharge of the guinea pig, examining specifically the histological and physiological changes that occur during a typical estrous cycle. In 1923 he turned to the cytological examination of the vaginal fluid of women as a way of detecting uterine cancer. In 1943 he published his findings after studying 179 cases of uterine cancer. His monograph Diagnosis of Uterine Cancer by Vaginal Smear treated a variety of physiological and pathological states, including abortion, amenorrhea, ectopic pregnancy, endometrial hyperplasia, menopause, the menstrual cycle, prepuberty, and puerperium. The Papanicolaou smear rapidly achieved wide acceptance as a means of cancer diagnosis.