目的　探讨错配修复基因PMS1在前列腺癌前病变 (前列腺上皮内瘤 ,PIN)中的表达及其与PIN的临床病理学行为的关系。方法　采用免疫组织化学法 ,检测PIN组织中PMS1的表达情况。结果　在全部 6例前列腺上皮内瘤中 ,PMS1的表达明显降低 ,随着PIN的分级增高 ,其降低越明显。结论　PMS1的丢失存在于前列腺癌的癌前病变 ,错配修复基因功能的丧失是前列腺癌形成的早期分子事件 ,参与了前列腺癌的发生与发展 Objective To investigate the expression of mismatch repair gene PMS1 in prostatic precancerous lesions (prostatic intraepithelial neoplasia, PIN) and its relationship with the clinicopathological features of PIN. Methods Immunohistochemistry was used to detect the expression of PMS1 in PIN tissue. Results The expression of PMS1 was significantly decreased in all 6 cases of prostatic intraepithelial neoplasia. The more significant the decrease of PMS1 was with the increase of PIN grade. Conclusion The loss of PMS1 exists in precancerous lesions of prostate cancer. The loss of function of mismatch repair genes is an early molecular event in the formation of prostate cancer and is involved in the occurrence and development of prostate cancer