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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)