Comparison of ovarian crescent sign and risk of malignancy index for prediction of ovarian malignancy in adnexal masses

Background: Objective of the study was to evaluate ovarian crescent sign (OCS) as a sonographic parameter for prediction of ovarian cancer in adnexal masses suspicious of ovarian malignancy and to compare it with risk of malignancy index (RMI).Methods: Presence of OCS and calculation of RMI was done for 50 cases of adnexal masses scheduled to undergo surgery taking histopathology as gold standard.Results: 18% (9/50) of adnexal masses were malignant. OCS was absent in all malignant lesions, giving a sensitivity and negative predictive value of 100%. OCS was present in 33/41 of benign masses (specificity 80.4%). Relation of OCS to mass size<10 cm and menopausal status was significant (p<0.001). RMI≥200 could not diagnose malignancy in 4/9 cases (sensitivity 55.5%). RMI had specificity and negative predictive value of 95.1% and 90.7% respectively. Combining OCS and RMI had a lower specificity. Sequential application using OCS as first node and RMI as second node failed to diagnose 44.4% (4/9) cases as malignant.Conclusions: OCS is cheaper, easy to perform and appears to be a better test than RMI to differentiate between benign and early-stage malignant ovarian tumors. It can be used for triaging patient for referral