TI-RADS 4: High Suspicion for Thyroid Malignancy
TI-RADS 4 indicates a thyroid nodule with high suspicion for malignancy, with approximately 32-84% positive predictive value for malignancy, requiring fine needle aspiration (FNA) biopsy for definitive diagnosis. 1, 2
Understanding TI-RADS Classification
The American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) is a standardized classification system that stratifies thyroid nodules based on ultrasound characteristics to:
- Predict probability of malignancy
- Guide management decisions
- Reduce unnecessary biopsies
The TI-RADS scoring system assigns points based on specific ultrasound features:
- Composition
- Echogenicity
- Shape
- Margins
- Echogenic foci (calcifications)
TI-RADS 4 Characteristics
TI-RADS 4 nodules typically demonstrate:
- Moderately suspicious ultrasound features
- Total point score of 7 or more on the ACR TI-RADS scoring system
- Higher risk of malignancy compared to TI-RADS 3 nodules
- May show features such as:
- Solid or predominantly solid composition
- Hypoechogenicity
- Irregular margins
- Taller-than-wide shape
- Microcalcifications
Management Recommendations for TI-RADS 4
For TI-RADS 4 nodules, management depends on size:
- ≥1.0 cm: FNA biopsy recommended
- 0.5-0.9 cm: FNA biopsy if ≥TR5, follow-up if TR4
- <0.5 cm: Usually observation rather than FNA
Clinical Significance and Risk Assessment
- TI-RADS 4 nodules have a significantly higher risk of malignancy than lower categories
- Studies show 32-84% positive predictive value for malignancy in TI-RADS 4 nodules 2, 3
- No TI-RADS 2 or 3 nodules were associated with Bethesda category V or VI (suspicious or malignant) diagnoses in research studies 4
- A high TI-RADS score (4-5) was indicative of papillary thyroid carcinoma in 29.4% of subcentimeter nodules 3
Pitfalls and Considerations
- Benign nodules may be misclassified as TI-RADS 4 due to overlapping features
- Histopathological features like fibrosis can mimic suspicious sonographic features 5
- Some benign nodules with fibrosis demonstrate "taller than wide" appearance, leading to higher TI-RADS scores 5
- Follicular epithelial hyperplasia in benign nodules may present with irregular margins and hypoechogenicity 5
Multimodal Approach to Improve Accuracy
For nodules classified as TI-RADS 4 where there is diagnostic uncertainty, additional ultrasound techniques may improve diagnostic accuracy:
- Shear wave elastography
- Super microvascular imaging
- Contrast-enhanced ultrasound
- Artificial intelligence-assisted interpretation 6
These approaches may help reduce unnecessary biopsies while still identifying clinically significant malignancies.