Note to first time users: this calculator aids in the use of the reporting system endorsed by the Korean Society of Thyroid Radiology (KSThR) and Korean Thyroid Association (KTA) for the ultrasound assessment of thyroid nodules. Other, to a varying degree different reporting systems such as the EU-TIRADS and ACR-TI-RADS have also been published. Please consult institutional and national guidelines to decide which system should you use. In any case it is recommended to indicate the exact reporting system (e.g. “K-TIRADS 4”) on the report instead of an ambiguous terminology (“TIRADS 4”).
Notes
This calculator is based on the guidelines of the Korean Society of Thyroid Radiology (KSThR) and Korean Thyroid Association (KTA), but is neither official, nor endorsed by the aforementioned organizations.
Categories in the K-TIRADS system
- K-TIRADS 1: no nodules present
- K-TIRADS 2: benign morphology (purely cystic/anechoic, comet tail artefact, spongiform)
- K-TIRADS 3 (low risk): partially cystic / isohyperechoic with no suspicious features
- K-TIRADS 4 (intermediate risk): as for K-TIRADS 3 but with any suspicious features or as for K-TIRADS 5 but without suspicious features
- K-TIRADS 5 (high risk): solid hypoechoic nodule with any of the suspicious features
Biopsy recommendations
- K-TIRADS 2: if a spongiform nodule is ≥20 mm FNA is recommended
- Although biopsy of K-TIRADS 2 nodules is not routinely recommended, it can become necessary if e.g. surgery or ablation therapy is required.
- K-TIRADS 3: ≥15 mm
- K-TIRADS 4: ≥10 mm
- K-TIRADS 5: ≥10 mm (>5 mm in select cases)
- Biopsy should be performed without regard to nodule size if nodal metastasis or extrathyroid tumor extension is suspected.
- The original publication of the K-TIRADS system contains a flowchart summarizing the categories and the defining features. It also has specific recommendations based on FNA results (Table 3).
Cervical lymph node assessment
- Benign features: normal hilar fatty echo and vascular pattern.
- Intermediate features: loss of normal hilar structure. FNA is recommended if short axis diameter is >5 mm.
- Suspicious features: cystic/necrotic change, micro or macrocalcification, hyperechogenicity and abnormal peripheral or diffuse vasculature. FNA is indicated if short axis diameter is >3 mm.
Signs of extrathyroid extension
- Capsular protrusion: bulging into the adjacent tissues causing the loss of the normal tissue boundaries.
- Capsular disruption: loss of the perithyroidal echogenic line where the thyroid mass contacts it.
- Capsular abutment: no tissue in between the thyroid mass and the thyroid capsule.
Estimated risk of malignancy
- 0–2% for K-TIRADS 2 (benign)
- 2.4–7.8% for K-TIRADS 3 (low suspicion)
- 13.4–33.7% for K-TIRADS 4 (intermediate suspicion)
- 66.1–79.6% for K-TIRADS 5 (high suspicion)
Practical points and definitions
- Solid nodule: nodule without any obvious cystic components.
- Predominantly solid nodule: nodule with minimal cystic changes (< 10%)
- Spongiform nodule: microcystic changes (>50%) in the isoechoic soft-tissue component.
- Nonparallel orientation: (taller-than-wide shape) is defined in both the axial and sagittal imaging planes in the K-TIRADS system.
- Several studies have demonstrated that K-TIRADS has a high sensitivity but lower specificity compared to the ACR-TIRADS and EU-TIRADS system, furthermore it has a higher rate of unnecessary biopsies.
- A noticeable difference compared to the other reporting systems is that K-TIRADS has no recommendations for follow-up. The reason is that active surveillance of small nodules without biopsy in preventing nodal/distant metastasis formation in papillary thyroid cancer has not been validated.
- Much like other thyroid nodule reporting systems K-TIRADS does not incorporate color Doppler or elastography into the nodule assessment.
- An excellent comparison of K-TIRADS, ACR-TIRADS, and EU-TIRADS can be found in this article (Table 1-2):
Last updated: 2021-09-13