Malignancy rate of cervical lymph nodes based on concordance of ultrasound and computed tomography imaging features in patients with thyroid cancer.

PURPOSE: This study analyzed the malignancy rate of lymph nodes (LNs) according to the concordance of ultrasound (US) and computed tomography (CT) imaging features in patients with thyroid cancer.

METHODS

A retrospective analysis was performed of 277 cytopathologically confirmed cervical LNs (53.1% malignant) from 228 patients with thyroid cancer who underwent US-guided biopsy and preoperative US and CT. Malignancy rates were calculated according to the concordance of US and CT imaging features by matching cortical hyperechogenicity or abnormal vascularity on US (US-echo-vascularity) with strong or heterogeneous enhancement on CT (CT-enhancement), cystic changes on US (US-cystic) with cystic changes on CT (CT-cystic), and echogenic foci on US (US-EF) with calcifications on CT (CT-calcification).

RESULTS

Malignancy rates were significantly higher in positively concordant cases across all imaging features compared to negatively concordant cases (US-echo-vascularity/CT-enhancement: 93.5% vs. 8.2%, P<0.001; US-cystic/CT-cystic: 94.4% vs. 41.3%, P<0.001; and US-EF/CT-calcification: 84.4% vs. 34.5%, P<0.001). Discordance in US-cystic/CT-cystic (96.3% vs. 94.4%, P=0.735) or US-EF/CT-calcification (86.0% vs. 84.4%, P=0.873) findings showed malignancy rates comparable to those for positively concordant cases. However, discordance in US-echo-vascularity/CT-enhancement resulted in a significantly lower malignancy rate than in positively concordant cases (66.8% vs. 93.5%, P<0.001). In this discordant group, CT demonstrated a higher diagnostic odds ratio (3.896 vs. 0.257, P=0.002) and higher sensitivity (81.1% vs. 18.9%, P<0.001) than US.

CONCLUSION

Positive US/CT concordance across all imaging features, as well as discordance in US-cystic/CT-cystic or US-EF/CT-calcification, strongly suggested LN metastasis. CT-enhancement was particularly reliable when discordant with US-echo-vascularity.