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Objective: To investigate the difference in the clinicopathologic and ultrasonic features between unifocal and multifocal papillary thyroid carcinomas. Methods: A total of 448 cases with papillary thyroid carcinoma undergone total thyroidectomy were enrolled during Jan. 2007 to Jan. 2019. Patients were divided into two groups which were unifocal tumor group (155 cases) and multifocal tumor group (293 cases). The difference in clinicopathologic and ultrasonic features between two groups were compared using χ2 test and non-parametric tests. Results: The pathological examination revealed that the multifocal tumors presented more microcarcinoma (72% vs 63%, P=0.049), lymph node metastasis （LMN） (56% vs 41%, P=0.004), capsular invasion (10% vs 3%, P=0.009) and less nodular goiter （42% vs 56%, P=0.003） than those of unifocal tumors. Comparing to unifocal tumors, the multifocal tumors occurred more in the middle dorsal and medial lateral side of the thyroid （P=0.029, P=0.008; P=0.002, P=0.011）, and their size measured with three diameters(vertical anteroposterior, left right diameters) was smaller (P=0.004, P=0.001, P=0.023) in ultrasonography. In addition, the multifocal group had less unclear boundary (67% vs 77%, P=0.013), heterogeneous internal echoes (79% vs 88%, P=0.009), calcification (50% vs 63%, P=0.010) and pos-terior echo change （18% vs 28%, P