OBJECTIVETo investigate the risks for occult carcinoma in contralateral nodules for unilateral papillary thyroid carcinoma.

METHODSThe study included 157 consecutive cases of unilateral papillary thyroid carcinoma with benign nodules in the contralateral lobe identified by preoperative ultrasound or fine-needle aspiration from January 2011 to December 2013. The patients received total thyroidectomies and neck lymph node dissections. The frequency and predictive factors for contralateral occult carcinoma in these patients were analyzed.

RESULTSA total of 68 patients (43.3%) had occult papillary thyroid carcinoma in the contralateral lobe and the maximum diameter of contralateral occult papillary carcinoma ranged from 0.1 to 1.2 cm, including ≤ 0.5 cm in 56 patients, 0.5-1.0 cm in 9 patients and >1.0 cm in 3 patients respectively. In univariate analysis, occult carcinoma in the contralateral lobe was associated with patient age (χ(2) = 7.266, P = 0.007) and pathologically multifocality in the ipsilateral lobe (χ(2) = 5.090, P = 0.024), but not with family history, tumor size, thyroid function, Hashimoto's thyroiditis, perithyroidal invasion, multifocality in the ipsilateral lobe, clinically or pathologically node-negative neck. In multivariate Logistic an analysis, age (OR = 1.054, P = 0.001) and multifocality in the ipsilateral lobe on final pathology (OR = 2.443, P = 0.021) were independent predictive factors for contralateral occult papillary thyroid carcinoma.

CONCLUSIONSOccult carcinoma is common in the contralateral "benign" nodules in patients with unilateral papillary thyroid carcinoma especially in young patients or the cases with multifocal tumors.