Influence of Tumor Number on Clinicopathologic Features and Outcomes of Patients With Papillary Thyroid Carcinoma.

<bold>Objectives: </bold>The purpose of this study was to investigate the significance of tumor number on clinicopathologic factors and outcomes of patients with papillary thyroid carcinoma (PTC).<bold>Methods: </bold>We retrospectively analyzed 667 patients with PTC. We compared clinicopathologic features of patients with a different tumor number. Cox proportional hazards model was used to analyze risk factors of recurrence.<bold>Results: </bold>In papillary thyroid microcarcinoma (PTMC), the increase in the number of tumor foci was related to a higher risk of minimal extrathyroidal extension (ETE) and lymphovascular invasion (P < .05). Patients with PTMC with four or more foci had a significantly higher risk of central lymph node metastasis (CLNM) and lateral lymph node metastasis (LLNM) than patients with solitary tumors (P < .05). Patients with macro-PTC with four or more foci and with three foci had a higher risk of gross ETE and lymphovascular invasion than patients with solitary tumors (P < .05). The increase in the tumor number was related to a higher risk of CLNM in macro-PTC (P < .05). The number of foci was the independent predictor of recurrence in patients with macro-PTC (P < .05).<bold>Conclusions: </bold>An increase in the number of tumors was associated with an increased risk of aggressive clinicopathologic features in PTMC and macro-PTC. The number of tumor foci could influence risk of recurrence in macro-PTC. [ABSTRACT FROM AUTHOR]