Predictive Factors of Lymph Node Metastasis in Follicular Variant of Papillary Thyroid Carcinoma

Background: Compared with conventional papillary thyroid carcinoma (PTC), follicular variant of PTC (FV-PTC) shows less aggressive behavior and better prognosis. Nonetheless, regional lymph node (LN) metastasis was found in 22.8% of FV-PTC patients. Because LN metastasis is a proven predictor of recurrence in PTC, it is important to assess LN metastasis in FV-PTC patients. Methods: We retrospectively reviewed 134 FV-PTC patients who underwent thyroidectomy with neck dissection. Results: Central LN metastasis (CLNM) and lateral LN metastasis (LLNM) were found in 50 (37.3%) and 16 (11.9%) patients, respectively. In the multivariate analysis for CLNM, male sex (adjusted OR 4.735, p = 0.001), nonencapsulated form (adjusted OR 2.863, p = 0.022), and tumor size >1.0 cm (adjusted OR 3.157, p = 0.008) were independent predictors of high prevalence of CLNM in FV-PTC patients. In the multivariate analysis for LLNM, microscopic extrathyroidal extension (ETE) (adjusted OR 3.939, p = 0.041) and CLNM (adjusted OR 13.340, p = 0.001) were independent predictors of high prevalence of LLNM in FV-PTC patients. Conclusions: Meticulous perioperative evaluation and prophylactic central neck dissection may be beneficial for FV-PTC patients with male sex, nonencapsulated form, and tumor size >1.0 cm. Moreover, cautious perioperative evaluation of lateral neck LN may be mandatory for FV-PTC patients with microscopic ETE and CLNM.