Risk factor for contralateral occult carcinoma in patients with unilateral papillary thyroid carcinoma.

Purpose: The extent of surgery necessary in patients with unilateral papillary thyroid carcinoma (PTC) on preoperative radiologic imaging is still in doubt. In this study, we aimed to define risk factors that could be indicators for malignant nodules in the contralateral thyroid lobe.

Methods: We included 438 patients who underwent total thyroidectomy between January 2011 and December 2014 at our institution. In this study, patients were divided into two groups according to the presence of contralateral occult carcinoma identified by postoperative pathological examination. We analyzed the clinicopathologic factors including characteristics of coexistent nodules in the contralateral lobe based on preoperative radiological imaging.

Results: A total of 96 patients (21.9%) had PTC in the contralateral lobe. There were no significant differences between patients with or without contralateral occult carcinoma with respect to gender, age, primary tumor size, central lymph node metastasis, extrathyroidal extension and stage. The presence of Hashimoto's thyroiditis was an independent predictive factor for contralateral occult carcinoma (P=0.01).

Conclusion: A risk factor for contralateral occult carcinoma in unilateral PTC patients is Hashimoto's thyroiditis. Therefore, more caution is needed when determining optimal surgical methods for PTC patients with Hashimoto's thyroiditis.