Table 2 Univariate and multivariate analyses for central lymph node metastasis in the training cohort. Abbreviations: HR, hazard ratio; CI, confidence interval

Age, years

 < 45

Reference

Reference

 ≥ 45

0.519

0.325–0.828

0.006

0.461

0.267–0.798

0.006

Sex

 Female

Reference

 Male

1.686

0.973–2.923

0.063

Tumor size, cm

 < 0.7

Reference

Reference

 ≥ 0.7

2.474

1.547–3.956

< 0.001

1.205

0.688–2.110

0.514

Multifocality

 No

Reference

 Yes

1.501

0.928–2.427

0.098

Laterality

 Unilateral

Reference

 Bilateral

1.610

0.911–2.845

0.101

Margin

 Smooth

Reference

 Irregular

1.254

0.768–2.048

0.365

Calcification

 Absent

Reference

Reference

 Presence

2.006

1.260–3.194

0.003

1.496

0.869–2.575

0.146

Capsule invasion

 Absent

Reference

Reference

 Present

2.731

1.196–6.238

0.017

2.885

1.108–7.514

0.030

Hypoechoic

 No

Reference

 Yes

1.158

0.530–2.528

0.713

Rad score (per 0.1 increment)

2.481

1.948–3.160

< 0.001

2.376

1.843–3.063

< 0.001