Abstract: Abstract Objective:. To study the expressions of TRβ1 mRNA and clinical significance in breast cancer.Methods：The expressions of TRβ1mRNA in 40 cases of breast cancer and 10 cases of normal tissue were detected and analysed by using reverse-transcription PCR (RT-PCR). Results：The TRβ1 gene was expressed in all normal breast tissue. By contrast, reduced expression of TRβ1was found in 34 of the 40 breast cancer tissue samples (85%). The expression levels of TRβ1 were significantly lower in cancer group than those of normal group (P < 0.05).The expressions of TRβ1mRNA were significantly related with the depth of invasion, lymph-node metastasis and TNM stage(P < 0.05). but not related with age (P ＞ 0.05)，. Conclusion： TRβ1 play an important role in invasion and metastasis of the breast cancer. Detection of TRβ1 may be a new target for cancer diagnosis to assess the severity of breast cancer.

Key words: breast cancer, TRβ1gene, mRNA, RT-PCR