Fig. 1Algorithm used in the Korean Thyroid Imaging Reporting and Data System for malignancy risk stratification based on solidity and echogenicity of thyroid nodules. Adapted from Shin et al. [9]. US, ultrasonography. aMicrocalcification, taller than wide shape, spiculated/microlobulated margin.
Table 1Sonographic Patterns, Risk of Malignancy, and FNA Guidance for Thyroid Nodules in the 2015 American Thyroid Association Guidelines
Sonographic pattern |
US features |
Estimated risk of malignancy, % |
FNA size cutoff (largest dimension) |
High suspicion |
Solid hypoechoic nodule or solid hypoechoic component of a partially cystic nodule with one or more of the following features: irregular margins (infiltrative, microlobulated), microcalcifications, taller than wide shape, rim calcifications with small extrusive soft tissue component, evidence of ETE |
>70–90a
|
Recommend FNA at ≥1 cm |
Intermediate suspicion |
Hypoechoic solid nodule with smooth margins without microcalcifications, ETE, or taller than wide shape |
10–20 |
Recommend FNA at ≥1 cm |
Low suspicion |
Isoechoic or hyperechoic solid nodule, or partially cystic nodule with eccentric solid areas, without microcalcification, irregular margin or ETE, or taller than wide shape |
5–10 |
Recommend FNA at ≥1.5 cm |
Very low suspicion |
Spongiform or partially cystic nodules without any of the sonographic features described in low, intermediate, or high suspicion patterns |
<3 |
Consider FNA at ≥2 cm observation without FNA is also a reasonable option |
Benign |
Purely cystic nodules (no solid component) |
<1 |
No biopsyb
|
Table 2Malignancy Risk Stratification according to K-TIRADS and FNA Indications
|
Category |
US feature |
Malignancy risk, % |
Calculated malignancy risk (%), overall (LV, HV) |
Calculated sensitivity for malignancy (%), overall (LV, HV) |
FNAa
|
5 |
High suspicion |
Solid hypoechoic nodule with any of 3 suspicious US featuresb
|
>60 |
79.3 (60.9, 84.9) |
51.3 (35.9, 56.7) |
≥1 cm (>0.5 cm, selective) |
4 |
Intermediate suspicion |
Solid hypoechoic nodule without any of 3 suspicious US featuresb or
Partially cystic or isohyperechoic nodule with any of 3 suspicious US featuresb
|
15–50 |
25.4 (15, 33.6) |
29.5 (29.9, 29.4) |
≥1 cm |
3 |
Low suspicion |
Partially cystic or isohyperechoic nodule without any of 3 suspicious US featuresb
|
3–15 |
7.8 (6, 10.3)c
|
19.2 (34.2, 13.9) |
≥1.5 cm |
2 |
Benignd
|
Spongiform Partially cystic nodule with comet tail artifact Pure cyst |
<3 <1 |
0 0 |
0 0 |
≥2 cm NA |
1 |
No nodule |
- |
- |
- |
- |
NA |
Table 3Results of Two Studies on Active Surveillance in Japan
Variable |
Ito et al. (2014) [4] |
Sugitani et al. (2010) [5] |
No. of patients |
1,235 |
230 |
Mean follow-up duration, mo |
60 |
60 |
Progression, % |
|
|
Size enlargement >3 mm |
|
|
5 yr |
5 |
7 |
10 yr |
8 |
|
LN metastasis |
|
|
5 yr |
1.7 |
1 |
10 yr |
3.8 |
|
Recurrence after delayed Op |
1/191 |
0/16 |