['The aim of this study was to detect the expression of hypoxia-inducible factor (HIF)-1α and HIF-2α in papillary thyroid carcinoma (PTC) compared with normal thyroid tissues.', 'The mRNA levels and protein levels of HIF-1α and HIF-2α were detected by real-time PCR and Western blot separately in 30 pairs of PTCs and normal thyroid cases. The protein levels were also detected by immunohistochemistry (IHC) using 92 samples of PTC group and 46 normal samples as control group for analyzing the biological and clinical significance of the expression of HIF-1α/HIF-2α.', "Real-time PCR results showed the mRNA level of HIF-1α and HIF-2α were significantly higher in PTC than normal group (P<0.001). Also, significantly higher positive rates (73%/65%) of HIF-1α and HIF-2α were observed in PTC compared with the control group (27%/35%) by IHC (P<0.01); the consistent results were gotten with Western blot. Although we did not find a significant correlation between the expression of HIF-1α and HIF-2α with gender, age, calcification, or Hashimoto's disease in the present study (P>0.05), both of their expressions were correlated to lymph node metastasis (P<0.05), capsular invasion (P<0.05), and TNM stage (P<0.05)."] Does expression of HIF-1α and HIF-2α correlate to biological and clinical significance in papillary thyroid carcinoma?