Patterns and Predictive Factors of Lateral Lymph Node Metastasis in Papillary Thyroid Microcarcinoma

Objective. To determine the incidence and patterns of and to evaluate the predictive factors for lateral cervical lymph node metastasis (LNM) in papillary thyroid microcarcinoma (PTMC). Study Design. Case series with chart review. Setting. Academic university hospital Subjects and Methods. From March 2007 to September 2010, a retrospective review was performed of 490 patients with PTMC who underwent total thyroidectomy and central lymph node dissection with or without lateral cervical lymph node dissection. The clinicopathologic results were reviewed, and the incidence and patterns of lateral cervical lymph node metastasis were analyzed. Results. The overall frequency of central and lateral LNM was 39.6% and 3.0%, respectively. The incidence of lateral lymph node metastasis in level IIa, III, IV, Vb, IIb, and Va was 46.7%, 53.3%, 73.3%, 6.7%, 6.7%, and 20.0%, respectively. Lateral LNM without central LNM was observed in 3 (0.6%) cases of PTMC. A multivariate analysis revealed that the predictive factors for the presence of lateral lymph node metastasis are male sex, increased tumor size, T4 stage, and pathologic central lymph node metastasis. Conclusion. Although lateral LNM was rare, the surgeon should perform thorough preoperative studies to look for lateral LNM in cases of PTMC if the patient is male, has a relatively larger tumor size, and has aggressive mass and also to look for the possibility of skip metastasis. Lymph node metastasis involving the spinal accessory chain (IIb) was not that rare, and careful level IIb lymph node dissection should be considered for patients who will undergo a modified radical neck dissection for lateral LNM.