Size of thyroid cancers does not correlate well with pre-operative thyroid nodule size on ultrasound

Introduction: Pre-operative thyroid ultrasound (TUS) helps risk-stratify patients with thyroid nodules.We evaluated the association between TUS size, pathologic papillary thyroid cancer (PTC) size, and extent of surgery pursued.Methods: A single-institution retrospective analysis was performed on patients > 18 years of age with a preoperative TUS from 2017 to 2022.Size comparisons were assessed using intra-class correlation (ICC).Results: In total, 252 patients with 261 nodules were included.Two-hundred and twenty-one (84.7 %) nodules were PTC.The average maximum diameter of nodules was 0.77 cm (+/-0.14cm) on TUS and 1.40 cm (+/-1.84cm) on pathology for PTC < 1 cm (p-value 0.31); ICC 0.0.The average maximum diameter of nodules was 2.03 cm (+/-0.78cm) on TUS and 1.67 cm (+/-1.13cm) on pathology for PTC 1 -4 cm (p = 0.001); ICC 0.30 (95 % CI 0.15 -0.46).The average maximum diameter of nodules was 5.29 cm (+/-1.21cm) on TUS and 3.58 cm (+/-2.36cm) on pathology for PTC > 4 cm (p < 0.001); ICC 0.05 (95 % CI -0.40 -0.51).Fifteen patients (45.5 %) with a TUS nodule > 4 cm and pathological PTC less than or equal to 4 cm underwent a total thyroidectomy.Conclusions: Pre-operative TUS of PTC > 1 cm overestimated the pathologic size of PTC.Nearly half of patients with a TUS nodule > 4 cm with pathologic PTC less than or equal to 4 cm underwent a total thyroidectomy.The size of nodules on pre-operative TUS should not dictate extent of thyroid resection alone.