Objective  To investigate the expression level of serum matrix metalloproteinase-13 (MMP-13) in patients with differentiated thyroid carcinoma (DTC) and its correlation with lung metastasis.

  Methods  A total of 70 DTC patients without lung metastasis were included in non-metastatic group, 46 DTC patients with lung metastasis were included in metastatic group, and 35 healthy subjects were included in control group. The changes of expression levels of MMP-13 in serum of three groups were detected and compared. Receiver operating characteristic (ROC) curve was drawn and the clinical diagnostic efficacy of serum MMP-13 was analyzed.

  Results  The expression levels of MMP-13 in the non-metastatic group and the metastatic group were significantly higher than those in the control group, and the expression level of MMP-13 in the metastatic group was significantly higher than that in the non-metastatic group (P < 0.01). Thyroid capsule invasion (OR=3.449), cervical lymph node metastasis (OR=6.501), mediastinal lymph node metastasis (OR=3.145) and MMP-13 levels (OR=4.369) were all independent risk factors for lung metastasis in patients with DTC. ROC curve results showed that the area under the curve (AUC) of serum MMP-13 expression levels in the diagnosis of lung metastasis in patients with DTC was 0.834 (95%CI, 0.743 to 0.924, P < 0.05). When the cut-off value was 142.58 pg/mL, the diagnostic sensitivity and specificity were 92.14% and 86.39%, respectively.

  Conclusion  The expression levels of MMP-13 in the serum of DTC patients is significantly increased, and MMP-13 can be used as a serological marker for the diagnosis of lung metastasis.