Abstract: Objective: To detect the expressions of CD133,cancer stem cells marker,and extracellular signal-regulated protein kinase 1(ERK1) in papillary thyroid carcinoma(PTC),and their correlations and clinicopathological significance.Methods: The expressions of CD133 and ERK1 in 68 samples of PTC tissue and 40 samples of nodular goiter tissue were detected by immunohistochemistry.Results: The positive rates of CD133 and ERK1 in PTC and nodular goiter tissues were 10.0% & 50.0% and 12.5% & 63.2%,respectively,the differences of which were statistically significant(P<0.01).The differences of the expression levels of CD133 in tumor grade,lymph node metastasis and TNM stage of PTC were statistically significant(P<0.05 to P<0.01).With the PTC worsening differentiation,lymph node transferring and clinical stage increasing,the positive rates of ERK1 increased(P<0.01).There was a positive correlation between the expression of CD133 and ERK1(P<0.05).Conclusions: The abnormal expressions of CD133 and ERK1 may be involved in the occurrence,development,invasion and metastasis of PTC.The early combination examination of CD133 and ERK1 has a certain clinical significance in the progression and prognosis of PTC.