OC021: Assessment of pattern recognition for the ultrasound diagnosis of an endometrioma

To describe the US characteristics of masses that, based on pattern recognition, are presumed to be an endometrioma.\ud\ud\udMethods\ud\ud\ud\ud\ud\ud\ud\udThe IOTA study included 3513 patients with an adnexal mass. All patients were scanned following the same US protocol. The US examiner had to suggest a specific histological diagnosis and to report with which level of confidence he made the diagnosis of benign or malignant. Masses with a presumed diagnosis of endometrioma were included. We considered the following three types of masses as typical for endometrioma: unilocular mass with ground glass appearance, unilocular-solid mass, ground glass and a papillary projection without internal flow, and a multilocular mass with ground glass echogenicitiy.\ud\ud\udResults\ud\ud\ud\ud\ud\ud\ud\udOut of 660 masses that were presumed to be endometriosis by the expert, 586 (88.8%) were proven endometriomas. 460 (78%) of them had typical features. Of the 74 misdiagnoses based on subjective impression, 64 (9.6%) proved to be benign and 10 (1.5%) malignant. Of the benign misdiagnoses, 31 (48%) had features typical for endometriomas. Histology was functional cyst (24), abscess (5), hydrosalpinx (5), dermoid (5), serous or mucinous cystadenoma (19), and other benign mass (6).\ud\ud\udOf the malignant misdiagnoses, 7 (70%) had US features typical for endometriomas and 3 were multilocular-solid tumors. 7 out of the 10 malignant masses were associated with normal CA 125 levels. Histologies were 3 endometrioid adenoca (2 stage I, 1 stage III), 1 stage III serous papillary adenoca, 5 stage I borderline tumors, and one uterine clear cell carcinoma. Sonologists were more confident about their diagnosis in the group that proved to be endometriomas (very confident 82%) than in the group with benign (very confident 59%) or malignant (very confident 10%) misdiagnoses.\ud\ud\udConclusions\ud\ud\ud\ud\ud\ud\ud\udExpert sonolgists can reliably diagnose endometriomas. However, even in “typical” unilocular cysts with ground glass appearance, the rate of unexpected malignancy is 1%