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 > or = 45 years and 13.5% < 45 years (p = .83). Bilateral PTC was found in 12.6% of patients with a primary tumour < or = 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.