ObjectiveTo detect expressions of PTEN and Ki-67 in primary thyroid cancer tissues and explore its clinical significances. MethodsThe expressions of PTEN protein and Ki-67 protein in 40 cases of paraffin-embedded tissues of primary thyroid cancer and the corresponding paracancerous tissues were detected by immunohistochemical method. The expressions of PTEN mRNA and Ki-67 mRNA in 14 cases of resected fresh tissues of primary thyroid cancer and the corresponding paracancerous tissues were detected by RT-PCR method. The relations between clinicopathologic characteristics and expression of PTEN protein or Ki-67 protein in the primary thyroid cancer tissues were analyzed. Results① The PTEN protein positive expression rate and the PTEN mRNA in the primary thyroid cancer tissues were significantly lower than those in the corresponding paracancerous tissues[35.0% (14/40) versus 60.0% (24/40), P<0.05; 0.225 7±0.036 3 versus 0.503 6±0.037 5, P<0.05], the Ki-67 protein positive expression rate and Ki-67 mRNA in the primary thyroid cancer tissues were significantly higher than those in the corresponding paracancerous tissues [72.5% (29/40) versus 42.5% (17/40), P<0.05; 1.212 1±0.042 1 versus 0.293 6±0.027 4, P<0.05]. ② The expressions of PTEN protein and Ki-67 protein were associated with the histological grading, pathological type, tumor stage, and presence of regional lymph node metastasis (P<0.05), which not associated with the patient's gender, age and integrity of tumor capsule or not (P>0.05). ③ The PTEN and Ki-67 protein expressions in the primary thyroid cancer tissues had a significantly negative correlation (rs=-0.605, P=0.000), which in the corresponding paracancerous tissues had no correlation (rs=-0.021, P=0.899). ConclusionPTEN and Ki-67 genes abnormally express in thyroid cancer tissue, which might be related with occurrence and development and its mechanism of primary thyroid cancer. Combination of two genes might contribute to identification of pathologic type, judge of biological behavior, and tumor stage of primary thyroid cancer, which might serve as a new target for diagnosis and treatment of it.