Predictors of metastasis in cervical indeterminate lymph nodes after thyroid cancer ablation by long-term ultrasound follow-up

To investigate the pattern of change over time and predictors for metastasis in indeterminate lymph nodes (LNs) among patients with thyroid cancer post-ablation. We enrolled patients who developed new cervical LNs after papillary thyroid carcinoma (PTC) ablation. Changes in the ultrasound characteristics of the indeterminate LN were recorded at months 1, 3, 6 and 12 after ablation. LN puncture pathology and long-term follow-up were standard of diagnosis. The indeterminate LNs were divided into benign and malignant groups, the differences between the two groups were compared, and the risk characteristics of malignant LNs were screened using generalized estimating equations (GEE). In total, we included 138 LNs from 99 patients, of which 48 were indeterminate LNs. When following up indeterminate LNs, non-cervical lymph node metastasis (non-CLNM) lesions demonstrated a statistically significant gradual decrease in volume (p = 0.012), though there was no significant change in the volume of CLNM lesions (p = 0.779). Compared to non-CLNM lesions, the diagnostic efficiency was the highest for CLNM lesions at 1-3 months after ablation, when the LN volume changed by −0.08 to 0.12 mL (p = 0.048). The third month after ablation became an important time point for review. Moreover, GEE analysis showed that microcalcifications, cystic changes, and vascularity were strongly associated with CLNMs (p = 0.004, p = 0.002, and p = 0.010, respectively). There is a pattern of volume change of indeterminate LNs after PTC ablation, which, together with microcalcifications, cystic changes, and vascularity, can be used as criteria for differentiating the benignity and malignancy of indeterminate LNs.