Multifocality of the primary tumor is a predictive factor for contralateral occult carcinoma in patients with unilateral papillary thyroid carcinoma

Purpose: To analyze the risk factors for occult contralateral carcinoma in the patients with unilateral thyroid papillary carcinoma (PTC). Methods: A retrospective review of the clinical data of PTC patients with total thyroidectomy from September 2012 to September 2014 in Zhejiang Cancer Hospital, was conducted to estimate the incidence of contralateral occult carcinoma of thyroid and to analyze the related risk factors. Results: A total of 300 patients with unilateral PTC were admitted in the present study. The rate of occult carcinoma in the contralateral lobe of thyroid was 18.3% (55/300). Contralateral occult carcinoma was not significantly associated with age, gender, the primary tumor size by ultrasonography and pathology, presence of Hashimoto's thyroiditis, capsular invasion, extraglandular extension, central lymph node metastasis, lateral cervical lymph node metastasis, or "benign" nodules in the contralateral lobe. The univariate analysis revealed that contralateral occult carcinoma was significantly increased in patients with multifocality of primary tumor (P=0.000). In multivariate analysis, mulifocality of primary tumor was an independent predictive factor for occult carcinoma in the contralateral lobe of thyroid gland (P=0.000, odds ratio=4.486). Conclusion: We demonstrated that the presence of mulifocality of primary tumor was an independent predictive factor for contralateral occult carcinoma in patients with unilateral PTC. The prediction of contralateral occult carcinoma in unilateral PTC according to pathological features, could be useful for determining the optimal extent of surgery.