How Many Contralateral Carcinomas in Patients with Unilateral Papillary Thyroid Microcarcinoma are Preoperatively Misdiagnosed as Benign?

The decision to perform a total thyroidectomy (TT) for unilateral papillary thyroid microcarcinoma (PTMC) with nodules in the contralateral lobe remains controversial. The aim of this study was to investigate the rate of contralateral carcinomas that are preoperatively misdiagnosed as benign. From October 2011 to October 2015, a total of 347 patients with unilateral PTMC and contralateral benign nodules who were treated with a TT at a single institution were enrolled. All patients underwent preoperative fine needle aspiration and ultrasonography (US). Clinicopathological features such as age, sex, laterality, tumor size, central lymph node metastases, capsular invasion, TgAb and TPOAb levels, Hashimoto's thyroiditis, nodule number in both lobes according to preoperative US, and primary carcinoma number in the final postoperative pathology report were all analyzed to investigate the rate and predictive factors of contralateral carcinoma. A total of 100 patients (28.9 %) were diagnosed with papillary thyroid carcinoma in the contralateral lobe. A multivariate analysis showed that tumor size, nodule number in the contralateral lobe, and multifocality of the primary tumor were all independent predictive factors of contralateral carcinoma in patients with unilateral PTMC and contralateral benign nodules. According to our findings, the rate at which contralateral carcinomas are preoperatively misdiagnosed as benign is 28.9 %. A TT is essential for unilateral PTMC with a primary tumor size > 5 mm, multifocal primary carcinomas or multifocal benign nodules in the contralateral lobe.