Prognostic significance of right subdiaphragmatic washing cytology in patients with endometrial cancer

Cancer cells in the right subdiaphragmatic lavage may reflect peritoneal dissemination, but its prognostic significance is unknown. This study investigated recurrence-free survival (RFS), overall survival (OS), and recurrence patterns in patients with curatively resected endometrial cancer by cytology collection site. Peritoneal cytology was collected at the beginning of surgery by washing the pelvic and right subdiaphragmatic cavity separately. The analysis included 465 patients with the median follow-up duration of 121 months. Of these, 62 (13%) patients had positive pelvic cytology and 22 (5%) patients had positive right subdiaphragmatic cytology. Patients positive for right subdiaphragmatic cytology were all positive for pelvic cytology, showing the worst RFS and OS among the study population. Multivariate analyses showed positive right subdiaphragmatic cytology, not pelvic cytology, significantly correlated with shorter RFS and OS when adjusted for clinicopathological factors. Patients with both pelvic and right subdiaphragmatic positive cytology had significantly higher peritoneal recurrence rates than those negative at both sites. However, patients with only positive pelvic cytology showed no significant difference in the recurrence rate. Our results suggest that the prognostic significance of peritoneal cytology may differ depending on the collection site in endometrial cancer and provide new insights to select patients for adjuvant therapy.