Prospective external validation of the 'ovarian crescent sign' as a single ultrasound parameter to distinguish between benign and malignant adnexal pathology

Abstract

Objective To determine the sensitivity and specificity of the 'ovarian crescent sign' (OCS)-a rim of normal ovarian tissue seen adjacent to an ipsilateral adnexal mass-as a sonographic feature to discriminate between benign and malignant adnexal masses. Methods The patients included were a subgroup of patients participating in the International Ovarian Tumor Analysis (IOTA) Phase 2 study, which is an international multicenter study. The subgroup comprised 1938 patients, with an adnexal mass, recruited from 19 ultrasound centers in different countries. All patients were scanned using the same standardized ultrasound protocol. Information on more than 40 demographic and ultrasound variables were collected, but the evaluation of the OCS was optional. Only patients from centers that had evaluated the OCS in ≥90% of their cases were included. The gold standard was the histological diagnosis of the adnexal mass. The ability of the OCS to discriminate between borderline or invasively malignant vs. benign adnexal masses, as well as between invasively malignant vs. other (benign and borderline) tumors, was determined and compared with the performance of subjective evaluation of ultrasound findings by the ultrasound examiner. Results The OCS was evaluated in 1377 adnexal massesfrom 12 centers, 938 (68%) masses being benign, 86(6%) borderline, 305 (22%) primary invasive and 48(3%) metastases. The OCS was present in 398 (42%) of938 benign masses, in 14 (16%) of 86 borderline tumors, in 18 (6%) of 305 primary invasive tumors (one malignantstruma ovarii, one uterine clear cell adenocarcinoma and16 epithelial carcinomas, i.e. four Stage I and 12 StageII-IV) and in two (4%) of 48 ovarian metastases. Hence, the sensitivity and specificity for absent OCS to identifya malignancy was 92% and 42%, respectively, and thepositive and negative likelihood ratios (LR+ and LR, respectively) were 1.60 and 0. 18. Subjective impressionperformed significantly better than the OCS. Sensitivityand specificity were 90% and 92%, respectively, LR+was 11.0 and LR was 0. 10. For discrimination betweeninvasive vs. benign or borderline tumors, the sensitivityfor absent OCS was 94%, the specificity was 40%, the LR+ was 1.58 and the LR was 0.14. Conclusion This study confirms previous reports that thepresence of the OCS decreases the likelihood of invasivemalignancy in adnexal masses. However it is a poordiscriminator between benign and malignant adnexalmasses. Copyright © 2010 ISUOG. Published by JohnWiley & Sons, Ltd.