Factors predictive of papillary thyroid micro-carcinoma with bilateral involvement and central lymph node metastasis: a retrospective study

Background: The optimal resection extent for papillary thyroid microcarcinoma (PTMC) remains controversial. The objective of the study was to investigate risk factors of bilateral PTMC and central lymph node metastasis (CLNM) to guide surgical strategies for PTMC patients. Methods: We retrospectively reviewed 211 PTMC patients who underwent total thyroidectomy (TT) and 122 clinical lymph node-negative (cN0) cases that underwent prophylactic central lymph node dissection (CLND) between 2010 and 2011. The frequency, pattern, and predictive factors for bilateral PTMC and CLNM in these patients were studied using univariate and multivariate analysis with respect to the following variables: age, gender, extrathyroidal extension (ETE), T stage, with Hashimoto thyroiditis (HT), tumor size and multifocality based on final pathology, and preoperative evaluation using ultrasonography (US). Results: Fifty-four of 211 (25.6%) patients had bilateral PTMC. In multivariate analysis, multifocality (P < 0.001, OR = 23.900) and tumor size >= 7 mm (P = 0.014, OR = 2.398) based on US were independent predictive factors for bilateral PTMC which was also independently associated with multifocality (P < 0.001, OR = 29.657) and tumor size >= 7 mm (P = 0.005, OR = 2.863) based on final pathology. Among 122 cN0 patients who underwent prophylactic CLND, we found 49.2% of patients had CLNM. CLNM was independently associated with men, age < 50 years and tumor size >= 7 mm based on final pathology or preoperative US. Conclusions: TT should be considered for PTMC patients who are found multifocality and tumor size >= 7 mm based on preoperative US. CLND need be considered in cN0 patients who are men, aged < 50 years or tumor size >= 7 mm based on preoperative US.