ToolsCalculators
IOTA Simple Rules for ovarian tumour risk
Ultrasound-based classification of an adnexal mass as benign, malignant, or inconclusive.
IOTA Simple Rules for ovarian tumour risk
Unilocular cyst
Benign (B) feature.
Solid component present, largest diameter <7 mm
Benign (B) feature.
Acoustic shadows present
Benign (B) feature.
Smooth multilocular tumour, largest diameter <100 mm
Benign (B) feature.
No blood flow on Doppler (colour score 1)
Benign (B) feature.
Irregular solid tumour
Malignant (M) feature.
Ascites present
Malignant (M) feature.
>=4 papillary structures
Malignant (M) feature.
Irregular multilocular-solid tumour, largest diameter >=100 mm
Malignant (M) feature.
Very strong blood flow on Doppler (colour score 4)
Malignant (M) feature.
ResultInconclusive - both or neither B and M features present
Simple Rules cannot classify this mass; refer for expert ultrasound assessment or a secondary model (e.g., ADNEX).
- B-features present
- 0
- M-features present
- 0
When to use
- Triaging an adnexal (ovarian) mass found on ultrasound as benign, malignant, or needing further specialist evaluation.
Formula
If only B-features (of 5) are present -> benign. If only M-features (of 5) are present -> malignant. If neither or both are present -> inconclusive (Simple Rules cannot classify).
Pearls and pitfalls
- About 20-25% of masses are unclassifiable by Simple Rules alone and need a secondary model (e.g., ADNEX) or expert ultrasound review.