Table 3 Univariate Cox proportional hazards regression models to evaluate clinicopathological factors as predictors of distant metastasis and recurrence

Age, year^a

1.00

0.93–1.07

0.9904

Sex

Female

Reference

Male

1.50

0.19–9.15

0.6617

Preoperative serum calcium level, mg/dl^a

1.67

0.97–3.43

0.0661

Preoperative intact PTH, pg/ml^a

1.00

0.99–1.00

0.1429

Surgery

Parathyroidectomy alone

Reference

Combined thyroidectomy and/or Ln dissection

0.96

0.09–0.12

0.9649

Tumor weight, mg^a

1.00

1.00–1.001

0.0189

Tumor diameter, mm^a

1.00

0.94–1.05

0.9885

Vascular invasion

Absent

Reference

Present

3.47

0.51–68.06

0.2159

Necrosis

Absent

Reference

Present

9.45

1.56–71.64

0.0163

Histological component cells

Chief cells

Reference

Oxyphil cells

1.17

0.16–23.24

0.8911

Ki-67 index, %^a

1.46

1.14–1.98

0.0041