Preoperative BRAF Mutation is Predictive of Occult Contralateral Carcinoma in Patients with Unilateral Papillary Thyroid Microcarcinoma

Background and Objective: The optimal resection extent for clinically unilateral papillary thyroid microcarcinoma (PTMC) remains controversial. The objective was to investigate risk factors associated with occult contralateral carcinoma, and put emphasis on the predictive value of preoperative BRAF mutation. Materials and Methods: 100 clinically unilateral PTMC patients all newly diagnosed, previously untreated were analyzed in a prospective cohort study. We assessed the T1799A BRAF mutation status in FNAB specimens obtained from all PTMC patients before undergoing total thyroidectomy (TT) and central lymph node dissection (CLND) for PTMC. Univariate and multivariate analyses were used to reveal the incidence of contralateral occult cancer, difference of risk factors and predictive value, with respect to the following variables: preoperative BRAF mutation status, age, gender, tumor size, multifocality of primary tumor, capsular invasion, presence of Hashimoto thyroiditis and central lymph node metastasis. Results: 20 of 100 patients (20%) had occult contralateral lobe carcinoma. On multi-variate analysis, preoperative BRAF mutation (p = 0.030, OR = 3.439) and multifocality of the primary tumor (p = 0.004, OR = 9.570) were independent predictive factors for occult contralateral PTMC presence. However, there were no significant differences between the presence of occult contralateral carcinomas and age, gender, tumor size, capsular invasion, Hashimoto thyroiditis and central lymph node metastasis. Conclusions: Total thyroidectomy, including the contralateral lobe, should be considered for the treatment of unilateral PTMC if preoperative BRAF mutation is positive and/or if the observed lesion presents as a multifocal tumor in the unilateral lobe.