Results: Among all dominant adnexal masses ≥100 mm, 157 (52% (95% CI, 47-58)) were classified as unilocular and 143 (48% (95% CI, 42-53)) as multilocular at ultrasound examination.Risk of malignancy in surgically removed unilocular and multilocular masses was 2% (95% CI, 0-4).All malignant tumours had the largest diameter of ≥100 mm.In total, six malignancies were found: 50% borderline tumours and 50% primary malignancies from other origin, namely from appendix -low grade appendiceal mucinous neoplasm (LAMN).All malignancies were stage 1A.None of restaging operation was required.Conclusions: The risk of malignancy in surgically removed unilocular and multilocular adnexal masses as described by ultrasound was just 2%.There is desired to improve assessment to recognise tumours of other origins.It may be possible allowing operate various size of unilocular and multilocular adnexal masses in unspecialised hospitals to shorten queues in oncological centres.