摘要细胞内微RNA（miRNA）参与了癌症的发生、发展，而细胞外miRNA作为生物学标志物的用途近年来也受到了广泛关注，不断有研究证实某些胞外miRNA的水平与患者对化疗药物的反应相关。文章从循环中肿瘤特异的胞外miRNA的产生途径、检测方法、化疗反应预测等方面对近年来的研究成果进行综述，认为体液中miRNA的检测是标志物研究中一个有前景的领域。但是循环miRNA主要来源于血细胞、内皮细胞及其他一些血流量较高的器官，肿瘤特异的miRNA表达信息容易被掩盖，仍然需要进一步标准化实验流程和加大样本量来提高相关研究的说服力。

abstractsIntra-cellular microRNA (miRNA) has been proved to participate in the occurrence and development of tumors. Whereas extra-cellular miRNA's function as a tumor biomarker has drawn more and more attention recently. Accumulating evidences indicate that the level of certain extra-cellular miRNA is related to patients' response to chemotherapy. This article reviews the recent researches such as generating pathway, detective method and the prediction of patients' response to chemotherapy of tumor-specific extra-cellular miRNA, indicating that the detection of miRNA in the body fluid is considered to be a promising field of biomarker study. However, circulating miRNA mainly comes from blood cells, endothelial cells and other organs with high blood volume, which means that tumor-specific miRNA can easily be submerged. On the other hand, standardized experiment process and enlarged sample size can help to improve the credibility of relevant researches.