The stratification of patient risk depending on the size and ratio of metastatic lymph nodes in papillary thyroid carcinoma

Background: The aims of this study were to identify the clinical significances of the size of metastatic lymph node (mLN) and LN ratio (LNR) and to attempt to create a risk stratification for papillary thyroid carcinoma (PTC) patients. Methods: We investigated the 435 PTC patients who underwent radioactive iodine (RAI) ablation treatment following thyroid surgery. The patients were classified into two groups (micrometastasis (pN1mic) ≤ 0.2 cm and macrometastasis (pN1mac) > 0.2 cm) and were stratified into the following three risk groups: group I (pN1mic, LNR ≤ 0.5); group II (pN1mic, LNR > 0.5 or pN1mac, LNR ≤ 0.5); and group III (pN1mac with LNR > 0.5). And then we investigated the association of the classified groups and variable clinicopathologic factors. Results: The clinical characteristics such as large tumor size, extrathyroidal extension, higher T stage, and greater number of mLN or LNR were significantly associated with pN1mac. The mean stimulated thyroglobulin levels were increased with the patient risk groups (p = 0.02). The recurrence-free survivals were significantly different between the stratified groups (p = 0.001). Conclusions: The patient groups I, II, and III may be referred to as low-, intermediate-, and high-risk groups. Clinicians should consider the possibility of recurrence, and the decisions about the application of RAI ablation based on the size of mLN and the patient's risk groups.