What are the key ultrasound features that differentiate between benign and malignant ovarian cysts?

Key ultrasound features differentiating benign from malignant ovarian cysts include cyst morphology, wall characteristics, internal structure, and vascularity. Benign ovarian cysts typically present as unilocular, thin-walled cysts with anechoic (clear) fluid and smooth borders, often without solid components or papillary projections NICE CKS. In contrast, malignant cysts often show complex features such as thick, irregular walls, presence of solid areas or papillary excrescences, multilocularity with thick septations, and increased blood flow on Doppler ultrasound indicating neovascularity NICE CKS.

Specifically, benign cysts like simple cysts or functional cysts are usually unilocular with no internal echoes, whereas malignant cysts tend to be multilocular-solid or predominantly solid with heterogeneous echogenicity Sayasneh et al. 2015. The presence of papillary projections and nodularity within the cyst is a strong predictor of malignancy Choi et al. 2016. Furthermore, Doppler ultrasound showing low-resistance, high-velocity blood flow within solid components supports malignancy suspicion Sayasneh et al. 2015.

UK guidelines emphasise that complex cysts with solid areas, papillary projections, or increased vascularity warrant urgent referral for specialist assessment due to higher malignancy risk NICE CKS. Recent literature supports these criteria and proposes algorithms incorporating these ultrasound features to improve diagnostic accuracy Choi et al. 2016Sayasneh et al. 2015. MRI may be used as an adjunct for further characterisation but ultrasound remains the primary modality for initial differentiation Park & Lee 2014.