Bilateral Papillary Thyroid Cancer and Associated Histopathologic Findings

Objective: To determine the incidence of bilateral papillary thyroid cancer (PTC) at total thyroidectomy (TT) and compare demographic risk factors (gender and age) and histopathologic findings (tumour size, extrathyroidal extension [ETE], T staging, and multifocality) between patients with PTC in both thyroid lobes and those with PTC limited to the ipsilateral lobe and/or isthmus. Design: Retrospective study. Setting: University teaching hospital. Methods: The pathology results of 1047 consecutive patients who underwent TT between 2002 and 2008 were reviewed. Statistical significance was obtained using the chi-square test. Main Outcome Measures: Incidence of bilateral PTC and its association with demographic risk factors and histopathologic findings. Results: Among 592 patients with PTC, 13.2% had bilateral PTC and 86.8% had unilateral and/or isthmian PTC. Bilaterality was present in 12.4% of women and 16.7% of men (p = .24) and in 12.9% of patients aged >= 45 years and 13.5% < 45 years (p = .83). Bilateral PTC was found in 12.6% of patients with a primary tumour <= 2 cm and 13.5% > 2 cm(p = .75); 23.6% of tumours with ETE demonstrated bilaterality compared to 9.7% without (p < .0001), and 8.7% of pT1 (p = .08), 9.2% of pT2 (p = .02), 23.0% of pT3 (p < .0001), and 12.5% of pT4 (p = .87) tumours were bilateral, respectively. Among bilateral PTC patients, 43.2% had multifoci in at least one lobe compared to 6.4% when nonbilateral (p < .0001). Conclusions: After TT, 13.2% of patients had bilateral PTC. No significant correlation was established between bilaterality and gender, age, and tumour size. Bilaterality was more commonly found in patients with ETE, advanced T stage, and at least one multifocal lobe.