Risk factors for metastasis in indeterminate lymph nodes in preoperative patients with thyroid cancer

To investigate the relevance of clinical and sonographic features as indicators of metastasis in indeterminate lymph node (LN), to determine possible indications for fine-needle aspiration (FNA). Consecutive patients who underwent US-guided FNA for sonographic indeterminate LNs from differentiated thyroid carcinoma between January 2014 and December 2018 were retrospectively reviewed. Indeterminate LNs were defined as LNs which had neither an echogenic hilum nor hilar vascularity in the absence of any suspicious finding in accordance with the Korean Society of Thyroid Radiology (KSThR) guidelines. Univariate and multivariate logistic regression analyses were performed to identify significant risk factors related to malignancy of indeterminate LNs. Of the 236 LNs in 212 patients enrolled in this study, 67 LNs (28.3%) were metastatic. The multivariate logistic regression analysis showed that the long diameter of LNs has a negative association with metastasis in indeterminate LNs and the sonographic features of extrathyroidal extension (ETE) and nonparallel orientation of the primary tumor are associated with metastasis in indeterminate LNs. The sensitivity and positive predictive value were increased when FNA was performed for LNs with primary tumors showing ETE or nonparallel orientation than when FNA was performed for LNs larger than 5 mm (59.7% and 40.4% vs. 11.94% and 15.69%). The size of LNs has a negative association with metastasis in indeterminate LNs. Performing FNA for indeterminate LNs in patients whose primary tumor shows ETE or a nonparallel orientation can improve the diagnostic performance and decrease the rate of unnecessary FNA. The size of lymph nodes was negatively related to the risk of metastasis in indeterminate lymph nodes. Extrathyroidal extension and a nonparallel orientation of the primary tumor were suggested as sonographic features predicting metastasis in indeterminate lymph nodes. The routine practice of FNA for large indeterminate lymph nodes detected during preoperative evaluation of thyroid cancer should be discouraged.