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Evaluation of clinical risk factors for predicting insidious right central and posterior right recurrent laryngeal nerve lymph node metastasis in papillary thyroid microcarcinoma patients (cN0): experience of a single center.

Background
Papillary thyroid microcarcinoma (PTMC), one specific subtype of papillary thyroid carcinoma (PTC) which measures less than 10 mm in maximum dimension, presents with a high risk of insidious lymph node metastasis escaping from preoperative examinations (cN0). Given the complications of lymph node dissection (LND) and metastasis risk, proper stratification of PTMC for performing prophylactic LND bears great importance.


Methods
From June 2015 to December 2017, 338 PTMC patients undergoing thyroidectomy were included in the present study. Potential risk factors, including age, gender, maximal tumor size, etc. were collected and analyzed for association with thyroid lymph node metastasis.


Results
Among the 338 patients, 87 patients (25.7%) presented with right central lymph node metastasis (CLNM) and 28 patients (8.3%) had posterior right recurrent laryngeal nerve lymph node metastasis (PRRLN-LNM). The maximal tumor was prone to occur at the middle part of the lower pole (35.3%) in patients with right CLNM, while the proportion of tumors located in the middle part of the upper pole (17.2%) was highest in PRRLN-LNM patients. Ages younger than 45 years old, male gender, and a tumor size of more than 0.5 cm were correlated independently with right CLNM and PRRLN-LNM. Presence of capsular invasion also had a significant association with the occurrence of PRRLN-LNM.


Conclusions
Ages younger than 45, male gender, and a maximal tumor size larger than 0.5 cm, in addition to capsular invasion, were independent risk factors for stratification of PTMC patients. PTMC patients with these clinical characteristics were suggested to receive prophylactic LND in their initial thyroid surgeries.