A comparative study of the risk of malignancy index and the ovarian crescent sign for the diagnosis of invasive ovarian cancer.

OBJECTIVE: To compare the value of the risk of malignancy index (RMI) and the ovarian crescent sign (OCS) in the diagnosis of ovarian malignancy.

METHODS: This was a prospective observational study of women with ultrasonographic diagnosis of an ovarian cyst. The RMI was calculated in all cases using a previously published formula (RMI = U (ultrasound score) x M (menopausal status) x serum CA125 (kU/L)). A value > 200 was considered to be diagnostic of ovarian cancer. The OCS was defined as a rim of visible healthy ovarian tissue in the ipsilateral ovary. Its absence was taken as being diagnostic of invasive cancer.

RESULTS: A total of 106 consecutive women were included in the study, of whom 92 (86.8%) had a benign ovarian tumor, five (4.7%) had borderline lesions and nine (8.5%) had an invasive ovarian cancer. The absence of an OCS diagnosed invasive ovarian cancer with a sensitivity of 100% (95% CI, 70-100%), specificity of 93% (95% CI, 86-96%), positive predictive value (PPV) of 56%, negative predictive value (NPV) of 100% and positive likelihood ratio (LR+) of 13.86 (95% CI, 6.79-28.29). This compared favorably with a sensitivity of 89% (95% CI, 57-98%), specificity of 92% (95% CI, 85-96%), PPV of 50%, NPV of 99% and LR+ of 10.78 (95% CI, 5.34-21.77), which were achieved using RMI > 200 (P < 0.01).

CONCLUSIONS: The RMI and the OCS are useful tests for discriminating between invasive and non-invasive ovarian tumors. The application of these tests in a sequential manner might improve the overall accuracy of ovarian cancer diagnosis.