Uterine papillary serous carcinoma (UPSC) represents 10% of endometrial carcinomas. Significant number of patients initially present with extrauterine disease. The role of adjuvant treatment in low stage, especially polyp-confined UPSC is controversial. This multi-institutional study evaluated the significance of positive pelvic washing (PW) and adjuvant treatment on disease recurrence in a setting of endometrial polyp-confined UPSC. Surgical pathology files from 3 institutions were searched for cases of endometrial polyp-confined UPSC. Following histologic review, cases were clinically staged as Stage I, without myoinvasion or lymphovascular invasion. Clinicopathologic characteristics, results of PW, and type of adjuvant therapy were recorded. Statistical analysis using the Kaplan-Meier method for survival and Fisher exact test were performed. Thirty-three patients were included in the study. All patients were diagnosed with polyp-confined UPSC. The size of the polyp ranged from 0.3 to 4.3 cm. PW was positive for tumor cells in 8/33 (24%) patients. Twenty-two patients (66.6%) received some type of adjuvant treatment. Six patients (18%) developed recurrent disease. There was no significant difference in disease-free survival in the patients receiving adjuvant treatment versus not (P=0.375). However, there was significant association (P=0.0013) between positive PW and disease recurrence. Data are conflicting whether positive PW affects prognosis in low-stage endometrial carcinomas. Our study showed that in UPSC, malignant cells can be present in PW without lymphovascular invasion or myoinvasion and may have negative prognostic implication. Our data also reflect the controversies in the role of adjuvant treatment in endometrium-confined UPSC.