Table 1.
Comparative significance of risk categories for current TI-RADS assessment systems (ACR—American College of Radiology [18], EU—European [19] and K—Korean [20]) and the recommendations concerning TN threshold sizes for fine needle aspiration (FNA) and follow-up.
| TI-RADS Category |
Meaning | Risk of Malignancy | Size Threshold for FNA (cm) | Size Threshold for Follow-Up (cm) |
|---|---|---|---|---|
| TR 1 | Benign (ACR) No nodule (EU, K) |
- | No FNA | No follow-up |
| TR 2 | Not suspicious (ACR) Benign (EU, K) |
<2% (ACR) 0% (EU) <3% (K) |
No FNA | No follow-up |
| TR 3 | Mildly suspicious (ACR) Low risk (EU, K) |
2–5% (ACR) 2–4% (EU) 3–15% (K) |
>2.5 (ACR) >2 (EU) >1.5 (K) |
>1.5 (ACR) >1 (EU) |
| TR 4 | Moderately suspicious (ACR) Intermediate risk (EU, K) |
5–20% (ACR) 6–17% (EU) 15–50% (K) |
>1.5 (ACR) >1.5 (EU) >1 (K) |
>1 (ACR) >0.5 (EU) |
| TR 5 | Highly suspicious (ACR) High risk (EU, K) |
>20% (ACR) 26–87% (EU) >60% (K) |
>1 (ACR) >1 (EU) >1 (K) |
>0.5 (ACR) All (EU) |