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Table 1 Key ultrasound features with clinical implications of the findings

From: Ultrasound in active surveillance for low-risk papillary thyroid cancer: imaging considerations in case selection and disease surveillance

Ultrasound feature Clinical implication: active surveillance Clinical implication: surgery
Nodule size As per study inclusion criteria
(< 2 cm in Clinicaltrials.gov: NCT03271892)
Nodule measurement Maximum dimension on an axial image, maximum dimension perpendicular to the axial measurement on the same image and the maximum longitudinal dimension on a sagittal image
Nodule location Ensure that PTC is identified and labeled accurately for follow-up, especially in patients with MNG and multiple similar sized nodules
Evaluation for extrathyroidal extension (ETE) Confined to the thyroid parenchyma Loss of perithyroid echogenic line at site of contact of PTC
Thyroid margin bulge without disruption of perithyroid echogenic line
Nodule relationship to the trachea  < 7 mm nodule irrespective of relationship to trachea
 ≥ 7 mm nodule if acute angle to the trachea  ≥ 7 mm if obtuse angle to the trachea
Nodule relationship to tracheo-esophageal groove (TEG)  < 7 mm nodule irrespective of relationship to TEG
 ≥ 7 mm nodule if thyroid rim present between the PTC and TEG Lacking normal thyroid rim between TEG and PTC or protrusion of nodule to TEG or posteriorly
Evaluation of lymph nodes No suspicious cervical lymph nodes Lymph node(s) suspicious for metastatic disease (require biopsy confirmation)
Nodule growth at follow-up  < 3 mm in any one plane  ≥ 3 mm in any one plane or maximal diameter
(> 3 mm in Clinicaltrials.gov: NCT03271892)