The definition of lymph node micrometastases in pathologic N1a papillary thyroid carcinoma should be revised

Background

The aim of this study was to identify the risk factors for structural recurrence with a focus on lymph node–related factors and to determine the optimal cutoff size of lymph node micrometastases in patients with pathologic N1a classical papillary thyroid carcinoma.

Methods

We included patients who underwent total thyroidectomy with central compartment lymph node dissection for classic papillary thyroid carcinoma with pathologic N1a classification.

Results

A total of 398 patients were followed up for a median of 131 months. Structural recurrence occurred in 17.3% of patients (69/398). The multivariate analysis reported the following independent risk factors for structural recurrence: tumor size >1.95 cm, bilaterality, lymphatic and/or vascular invasion, a maximum diameter of the metastatic lymph node focus >3.5 mm, distribution of metastatic lymph node foci size >3.0 mm, and ≥4 metastatic lymph nodes.

Conclusion

The newly proposed cutoff of 3.5 mm for a definition of lymph node micrometastasis in pathologic N1a papillary thyroid carcinoma patients can reclassify the risk estimates of structural recurrence, thus modifying postoperative management plans and follow-up strategies.