Objective  To analyze the expression of three microRNAs (miRNAs) in the serum and plasma of breast cancer patients and to obtain the relationship between the serum and plasma of these patients. Moreover, the current study aims to explore the possibility of miRNA in plasma as a marker for breast cancer.

  Methods  The blood preparations of 31 cases that were registered in the Department of Thyroid and Breast Surgery, Huai'an No. 1 People's Hospital between December 2010 and March 2011 were enrolled based on the inclusion criteria. The nonanticoagulated and anticoagulated blood were sampled to extract serum and plasma, and then miRNA was isolated from the serum and plasma. The expression levels of miR-31, miR-155, and miR-200c in the serum and plasma were measured using real-time quantitative polymerase chain reaction (qPCR) analysis.

  Results  The expression levels of the three miRNAs in the serum were similar to those in the plasma. The expression level of miR-155 was upregulated and the expression of miR-200c was downregulated in the plasma of breast cancer patients compared with the patients without breast cancer. The expression of miR-31 between the two groups had no significant differences. On the other hand, the expression level of miR-155 had a close correlation with breast tumor size, breast cancer staging, lymph node metastasis, and the status of ER and PR. The expression of miR-200c was also closely correlated with the factors mentioned above, except for the status of PR. The expression of miR-31 was upregulated with the size of breast cancer, and had no distinct correlation with the other factors mentioned above.

  Conclusion  The current study demonstrated that the expression of miR-31, miR-155, and miR-200c between serum and plasma was similar. Moreover, the expression had close correlations with the clinicopathologic features of breast cancer, indicating that miRNA can be used as a potential marker for breast cancer.