How Many Contralateral Papillary Thyroid Carcinomas Can Be Missed?

Background When surgeons decide to perform lobectomy as the treatment of papillary thyroid carcinomas (PTCs), they must consider the possibility of contralateral cancer. We wanted to determine the incidence of bilateral PTCs (bPTCs) and analyze their characteristics. We also wanted to determine how many patients with bPTC were missed preoperatively. Methods From January 2007 to May 2011, a total of 466 patients with PTC who were treated by total thyroidectomy at a single institution were enrolled. Patients were divided into two groups based on bilaterality. The patients with bPTCs were further investigated regarding the preoperative presence of the contralateral tumor. Results Bilaterality was seen in 29.8 % of PTC patients. In all, 36.8 % of PTCs ≥1 cm, and 25.7 % were papillary thyroid microcarcinomas (PTMCs). The presence of PTC in the contralateral lobe was missed in 15.8 % of bPTCs and in 21.3 % of bPTMCs. The rates of preoperatively nondetected contralateral cancer were 4.7 and 5.5 % for PTCs and PTMCs, respectively. Tumor size and multifocality were factors associated with bilaterality ( p = 0.014 and p