Risk of thyroid malignancy and biopsy indications based on the ultrasonographic ACR-TIRADS criteria

Table 6.7-1. Risk of thyroid malignancy and biopsy indications based on the ultrasonographic ACR-TIRADS criteria
TIRADS category	Malignancy suspicion	Risk of malignancya	Requirement for FNAB	Recommended imaging follow-up after benign biopsy results
TIRADS 1 (1 point)	Benign	0.3%	No	None
TIRADS 2 (2 points)	Not suspicious	1.5%	No	None
TIRADS 3 (3 points)	Mildly suspicious	4.8%	Yes, if nodule size >2.5 cm	Follow-up in 1, 3, and 5 yearsb
TIRADS 4 (4-6 points)	Moderately suspicious	9.1%	Yes, if nodule size >1.5 cm	Follow-up in 1, 2, 3, and 5 yearsb
TIRADS 5 (>6 points)	Highly suspicious	35%	Yes, if nodule size >1.0 cm	Consider repeat FNA in 12 months and annual follow-up for up to 5 yearsb
a Risk of malignancy based on J Am Coll Radiol. 2017 May;14(5):587-595. b Significant interval enlargement warranting repeat FNAB is defined as increase >20% and >2 mm in 2 dimensions; or >50% increase in volume using the ACR-TIRADS thyroid nodule volume calculator (www.thyroid.org).
ACR-TIRADS; American College of Radiology Thyroid Imaging and Reporting System; FNAB, fine-needle aspiration biopsy.