Impact of Clinicopathologic Factors on Subclinical Central Lymph Node Metastasis in Papillary Thyroid Microcarcinoma

Purpose: We evaluated whether the clinicopathological factors of papillary thyroid microcarcinoma (PTMC), especially tumoe size, are associated with subcinical central lymph node metastasis. Materials and Methods: A total of 160 patients diagnosed with PTMC who underwent total thyroidectomy with bilateral central lymph node dissection were enrolled in this study. All patients were clinically lymph node negative PTMC. Patients were divided into 2 groups according to the size of tumor (<= 5 mm vs. >5 mm). Clinicopathologic risk factors for subclinical central lymph node metastasis were analyzed. Results: Subclinical central lymph node metastasis was detected in 61(38.1%). Patients with tumors <= 5 mm had a lower frequency of extrathyroidal extension, multifocality and subclinical central lymph node metastasis. On multivariate analysis, only male and tumor size >5 mm were independent predictors of subclinical central lymph node metastasis; age, multifocality, bilaterality, extrathyroidal extension, lymphvascular invasion and lymphocytic thyroiditis were not. Conclusion: In this study, male and tumor size >5 mm were two independent predictive factors for subclinical central lymph node metastasis in PTMC. These are easier factors to assess before surgery than other factors when planning the central lymph node dissection. However, further long-term follow-up studies are needed to confirm the prognostic significance of subclinical central lymph node metastasis in PTMC.