EP23.40: Experience with the modified benign descriptor four in the diagnosis of unclassified benign adnexal masses

To describe the experience with the modified benign descriptor (MBD) four in the diagnosis of unclassified benign adnexal masses. Ambispective observational study based on ultrasound data collected at a University Hospital with a gynecologic oncology unit between 2012 and 2023. Two IOTA-certified level III gynecologists classified adnexal masses using the MBD. The main result was the correct classification of unclassified benign adnexal masses, based on the fourth descriptor of the MBD (MBD 4). Histopathology was used as the diagnostic reference standard. A descriptive analysis was performed. A total of 1,047 adnexal masses were assessed, of which 656 (62.6%) were included when they met the classification criteria for their evaluation based on MBD. 218 masses were diagnosed as unclassified benign adnexal masses by the MBD 4, of which 215 (98.6%) corresponded to benign masses by histopathology. The remaining 1.4% (3/218) were false negatives, and the diagnoses that caused confusion were: one borderline serous tumour and one mucinous adenocarcinoma that presented histological changes due to torsion, and one borderline tumour that, despite showing benign features, underwent cystectomy due to a history of doubling in size and previous resection of a borderline tumour in the same ovary. In our experience, the MBD 4 has the ability to classify the majority of benign adnexal masses as benign.