Subclinical lymph node metastasis in papillary thyroid microcarcinoma: A study of 551 resections

Background: In clinically node-negative papillary thyroid microcarcinoma (PTMC), the frequency of subclinical lymph node metastasis (LNM) in the central cervical compartment (subclinical central LNM) has been reported to be as great as 65%. Routine prophylactic central compartment lymph node dissection (CLND) has been debated, because the risk of operative complications might outweigh its prognostic benefit. We aimed to study clinicopathologic factors associated with subclinical central LNM to be considered for determination of prophylactic CLND. Methods: A total of 551 patients diagnosed with clinically node-negative PTMC from 2005 to 2009 were included. All patients underwent total thyroidectomy (TT) and prophylactic CLND. Clinicopathologic risk factors of subclinical central LNM were analyzed. In addition, we investigated recurrences and postoperative complications after TT and CLND. Results: Among the 551 patients, 202 (37%) had subclinical central LNM. On univariate and multivariate analyses, male gender, tumor multifocality, and extrathyroidal extension were independently predictive of subclinical central LNM. During 3-year follow-up, there were no recurrences in the central cervical compartment. The frequency of permanent hypocalcemia and permanent vocal fold palsy were 1.1% and 1.3%, respectively. Conclusion: Frequency of subclinical central LNM was high in PTMC. It was managed effectively with prophylactic CLND. In addition, prophylactic CLND did not cause significant permanent morbidities. We recommend that clinicopathologic features, such as male gender, tumor multifocality, and extrathyroidal extension, be considered for determination of prophylactic CLND in patients with PTMC.