Table 4.

Modality of evaluation and classification of MTCs adopted by those five studies in which no RSS/TIRADS was used

Ref.	First author	Procedure to re‐evaluate US images	Procedure to assess MTCs as suspicious or not
[26]	Wang	2 sonographers with more than 10 years of experience reviewed US images blinded to clinical data, other imaging findings, and pathology results.	Malignant US features were irregular margin, marked hypoechogenicity, microcalcifications, and taller‐than‐wide shape.
[32]	Cho	Retrospective review of US images was performed by 2 radiologists with 5 and 15 years of experience blinded to pathologic results.	Malignant features were marked hypoechogenicity, microlobulated or irregular margins, microcalcifications, and taller than wide shape.
[35]	Trimboli	US images were reviewed by 4 reviewers with more than 10 years of experience in thyroid US.	MTCs were classified according to a 5‐class system. 45 Nodules with ≥3.5 were regarded as suspicious.
[41]	Fukushima	Not detailed	MTCs were classified according to a 5‐class system. 45 Nodules with ≥3.5 were classified as suspicious.
[42]	Boér	Not detailed	Not detailed

Abbreviations: MTC, medullary thyroid carcinoma; RSS, risk stratification system; TIRADS, Thyroid Imaging Reporting And Data System; US, ultrasound.