Expression and Tissue Distribution of MicroRNA-21 in Malignant and Benign Breast Tissues>.

Background/Aim: miR-21 is a common OncomiR in human cancer. The present study analyzed the distribution and expression of miR-21 in breast tumor tissues so as to examine the role of miR-21 in the carcinogenesis of breast cancer. Materials and Methods: Sixteen malignant and 10 benign breast tissue specimens were analyzed using a miRNA chromogenic in situ hybridization (CISH) assay. The locations of miR-21 CISH-positive cells in breast tissues were observed and its expression level was semi-quantified by ISH scoring. Results: Positive in situ staining of miR-21 was detected in the cytoplasm of malignant epithelial cells in most of the high-grade infiltrating ductal carcinoma specimens. miR-21-positive spindle-like cells were found to surround tumor cell islands. High miR-21 ISH scores were correlated with positive lymph node status. miR-21 expression was low in most types of benign breast tissues. Conclusion: miR-21 is a potential biomarker for breast cancer prognosis.