The Risk of Malignancy Index (RMI) is the current standard in differentiating benign from malignant adnexal masses. The simple ultrasound-based rules as a first stage triage test followed by either subjective assessment by an experienced ultrasound examiner or DW-MRI in case the simple rules are inconclusive, is the test of comparison. Both the RMI and the simple rules will be performed in the regional hospitals and MUMC+ by general gynaecologists during the same ultrasound scan. Only when the simple rules are inconclusive the patient will be referred to the MUMC+ for a second stage test. From previous publications it can be deducted that this will be in approximately 20% of patients. Approximately 80% of patients will not need any additional second stage test.