Predictive factors of contralateral occult carcinoma in patients with papillary thyroid carcinoma: a retrospective study.

Background: The surgical approach toward unilateral papillary thyroid carcinoma (PTC) has been in controversy. One of the concerns is the existence of contralateral occult carcinoma, which could cause relapse and even lead to re-operation if not dealt with. This study aims to find out risk factors related to contralateral occult PTC, in order to facilitate in surgical approach decision for PTC. Methods: A total of 921 PTC patients who underwent total/near-total thyroidectomy and central lymph node dissection (CND) with/without lateral lymph node dissection (LND) from January 2014 to Sept 2017 in Guangdong General Hospital were assessed retrospectively. The relations between contralateral occult PTC and clinicopathologic characteristics of PTC were analyzed by univariate and multivariate logistic regression. Results: The incidence of contralateral occult carcinoma in patients with PTC was 16.7% (154 of 921 cases). Univariate analysis showed that multifocality of the primary carcinoma (P=0.000), lymph node metastasis (P=0.001), pathologic tumor size (P=0.014) and contralateral benign nodule (P=0.000) were significantly associated with the increased incidence of contralateral occult PTC. No significant correlations were found between contralateral carcinoma and other variables such as gender (P=0.338), age (P=0.283), BRAF mutation (P=0.187) or extrathyroidal extension (P=0.423). Multivariate logistic regression analysis revealed that contralateral benign nodule (P=0.000), multifocality (P=0.000) and lymph node metastasis (P=0.009) were independent predictors of bilateral PTC of patients whose pre-operation ultrasound (US) show a unilateral carcinoma. Conclusions: Lymph node metastasis, contralateral benign nodule and multifocality are independent predictors of contralateral occult PTC. For unilateral PTC patients with one or more of these factors, total/ near-total thyroidectomy should be considered when making surgical approach decisions.