MicroRNA And Histopathological Characterization Of Pure Mucinous Breast Carcinoma

Objective:Pure mucinous breast carcinoma (PMBC) is an uncommon histological type of breast cancer characterized by a large amount of mucin production. MicroRNA (miRNA) is a large class of small noncoding RNA of about22nt involved in regulation of various biological processes. In this study, we want to dig out the miRNA expression profile in PMBC.Methods:MiRNA expression profiles in11PMBC were analyzed by miRNA-microarray and real time PCR. Thirty-one PMBC and twenty-seven invasive ductal carcinoma of no special types (IDC-NSTs) were assessed by immunohistochemistry using antibodies against ER, PR, HER2, Ki67, Bcl-2, p53, PCNA and CK5&6.Results:1.MiRNA Expression Profile in Pure Mucinous Breast Carcinoma.Tissue samples of11pure mucinous breast carcinoma and the corresponding normal tissues were obtained from patients who underwent breast cancer surgery. Two microarray hybridization studies were performed on a pair of PMBC-derived and matching adjacent normal tissue-derived RNA. To validate the miRNA-array results in a larger series of patients, we employed real time PCR to analyze the expression of miRNA in other10PMBC. The results showed that miR-143and miR-224-5p were significantly downregulated in pure mucinous breast carcinoma tissues compared to their corresponding normal tissues.MiR-143and miR-224-5p have been reported to be dysregulated in many kinds of cancers including prostate cancer, colon cancer, bladder cancer, renal cancer and hepatocellular carcinoma. Here for the first time we found these two miRNAs were downregulated in PMBC and this may help us to further understanding the molecular mechanism underlying this type of breast cancer.2.1mmunohistochemical Analysis of Pure Mucinous Breast Carcinoma. The histopathological and immunohistochemical features of pure mucinous breast carcinoma are summarized. The vast majority of PMBCs were of low cell proliferation rates (Ki67labeling), high ER positive rate (n=27/31), high PR positive rate (n=28/31), low HER-2positive rate (n=0/31) and could be classified as luminal A according to the criteria of Nielsen et al. The representative micrographs of immunohistochemical feature of PMBC were present.3. Comparison of Immunohistochemical Features between PMBC and IDC-NST.When comparing with invasive ductal carcinoma of no special types (IDC-NSTs), PMBC showed a significantly high ER positive rate (p<0.001), low HER-2positive rate (p<0.001) and low cell proliferation rates (Ki67labeling, p<0.001). Our result of ER staining is consistent with the former immunohistochemical findings of other groups. However, Ki67labeling result is in direct conflict with the finding of Lacroix-Triki et al. This earlier manuscript demonstrated that there was no different of Ki67labeling rates between PMBC and IDC-NST. The conflict may come from different patient selection. Lacroix-Triki et al chose ER matched PMBC and IDC-NST patients to carry out immunohistochemical staining.Conclusion:To our knowledge, this is the first study to demonstrate the miRNA expression profile of pure mucinous breast carcinoma and our finding may lead a further understanding of this type of breast cancer.