← All patterns
Adnexal cystic mass
GUUS / MRI
A cystic lesion of the ovary/adnexa. Internal content, wall/septal thickness and vascularity (O-RADS) stratify malignancy risk.
Differential
Functional / simple cyst
common- •Thin-walled anechoic unilocular cyst, no solid component
- •Premenopausal; resolves on follow-up
Haemorrhagic cyst
common- •Reticular/fishnet internal echoes with retracting clot
- •No internal vascular flow; involutes over 6–12 weeks
Endometrioma
common- •Homogeneous low-level ("ground-glass") echoes
- •T1 hyperintense with T2 shading on MRI
- •No enhancing solid nodule
Mature cystic teratoma (dermoid)
common- •Fat with fat-fluid level and calcification
- •Rokitansky nodule, echogenic with acoustic shadowing
- •Signal drops on fat-saturated MRI
Cystadenoma
less-common- •Serous: unilocular thin-walled; Mucinous: multilocular with variable fluid
- •Thin septa, no solid enhancing nodularity
Ovarian cystadenocarcinoma
less-common- •Thick irregular septa/walls with enhancing solid nodules
- •Ascites and peritoneal deposits; raised CA-125
- •Papillary projections with vascular flow
Key discriminators
- •Enhancing solid component / papillary projections (malignancy)
- •Fat (dermoid) vs ground-glass echoes (endometrioma)
- •Wall and septal thickness
- •Internal colour-Doppler vascularity
- •Ascites and CA-125
Work-up / next steps
- 1.Apply O-RADS ultrasound/MRI risk stratification
- 2.Multiparametric pelvic MRI for indeterminate lesions
- 3.Interval US for probable functional/haemorrhagic cysts
- 4.Gynae-oncology referral and CA-125 for O-RADS 4–5
References
- ACR O-RADS US and MRI.
- Radiopaedia: Ovarian cystic lesions.
Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.