中文摘要：

循环核酸是一种细胞外游离状态的核酸，肿痛患者血浆／血清中存在循环DNA、RNA和微RNA，具有片段小和含量低的特点。采用酚一氯仿抽提、硅胶或者磁珠载体分离法可提取微量的核酸片段，运用荧光分光光度法和PCR技术可观察循环核酸的改变。循环核酸检测可作为一种无创性的检测手段，应用于临床上肿瘤的早期诊断与鉴别、预后判断及疗效观察。

英文摘要：

Circulating nucleic acids in plasma or serum of cancer patients include circulating DNA, RNA and microRNA, which are characterized by small fragment and low content. Phenol-chloroform, silica gel and magnetic bead are often employed to extract the fragments of circulating nucleic acid, whose quantitative and qualitative changes were analyzed by fluorospectrophotometry and PCR respectively. Circulating nucleic acids are going to find their way of non-invasive methods in the early diagnosis aad differentiation, prognostic evaluation and monitoring of tumors.