The International Ovarian Tumour Analysis (IOTA) group ultrasound rules for ovarian masses are a simple set of ultrasound findings that classify ovarian masses into benign, malignant or inconclusive masses. These rules apply to masses that are not a classical ovarian mass (e.g. corpus luteum, endometrioma, dermoid cyst), which have pathognomonic imaging features.
Masses can be classified as either benign or malignant using simple ultrasound features. Ovarian masses that cannot be classified (~25% of ovarian masses) into either group are classified as "inconclusive" and further evaluation by a specialist in ovarian imaging is recommended.
If an ovarian lesion has at least one of these features and no malignant features it can be confidently considered benign 1:
- unilocular cyst
- smooth multilocular tumour <10cm
- solid component <7 mm in diameter
- acoustic shadows
- no detectable Doppler signal
If an ovarian lesion has at least one of these features and no benign features it can be confidently considered malignant 1:
- irregular solid tumour
- irregular multilocular mass >10 cm in diameter
- ≥4 papillary structures
- high Doppler signal
Treatment and prognosis
When the rules can be applied (~75% of masses), there is a sensitivity of ~90% and a specificity of ~95%, which is similar to subjective expert evaluation 1.
- 1. Timmerman D, Ameye L, Fischerova D et-al. Simple ultrasound rules to distinguish between benign and malignant adnexal masses before surgery: prospective validation by IOTA group. BMJ. 2010;341 (dec14 1): c6839. doi:10.1136/bmj.c6839 - Free text at pubmed - Pubmed citation
- 2. Kaijser J, Bourne T, Valentin L et-al. Improving strategies for diagnosing ovarian cancer: a summary of the International Ovarian Tumor Analysis (IOTA) studies. Ultrasound Obstet Gynecol. 2013;41 (1): 9-20. doi:10.1002/uog.12323 - Pubmed citation
- 3. Twickler DM, Moschos E. Ultrasound and assessment of ovarian cancer risk. AJR Am J Roentgenol. 2010;194 (2): 322-9. doi:10.2214/AJR.09.3562 - Pubmed citation