Table 2:

The Duke 3-tiered system for CT, MRI, or PET-detected thyroid nodules

Category	Criteria for Categories	Recommendations
Risk category 1: Highly suspicious for malignancy	PET avid thyroid nodule	Strongly consider work-up with ultrasound for any size nodule
	Suspicious lymphadenopathy^{^a}
	Extrathyroid spread with or without signs of vocal cord palsy on side of nodule
	Lung metastases
Risk category 2: Indeterminate with risk factor of young age	Age <35 years	Consider work-up with ultrasound if ≥1 cm in adults
	Age <35 years	Consider work-up with ultrasound for any size in pediatric patients
Risk category 3: Indeterminate without risk factors	Age ≥35 years	Consider work-up with ultrasound if ≥1.5 cm

Note:—Intended for management of incidental thyroid nodules in low-risk patients.
↵a Suspicious lymph nodes are defined as nodes >10 mm in short axis (with the exception of jugulodigastric lymph nodes, which were permitted to be up to 15 mm in short axis), or nodes that contained either calcifications, cystic components, or irregular margins.