Altered Expression of miR-146a-5p and Bcl-2 in Oncocytic Carcinoma of the Breast: A Case Report

Abstract Background: Oncocytic carcinoma of the breast is extremely rare, and its molecular profile is poorly understood. The distinctive feature of oncocytic carcinoma of the breast is that the granular eosinophilic cytoplasm contains numerous mitochondria. Recently, microRNA-146a-5p has been identified as a contributor to carcinogenesis and as a mitochondria-related microRNA, which regulates the mitochondrial function affecting Bcl-2. Bcl-2 plays a role in mitochondrial apoptosis.Case presentation: We report the clinical features, histopathological features, and immunohistochemical and molecular findings of oncocytic carcinoma of the breast in a 76-year-old woman. Immunohistochemistry studies revealed that the tumor cells were positive for antimitochondrial antibody but negative for gross cystic disease fluid protein 15, which confirmed the diagnosis. For molecular profiling, expression of microRNA-146a-5p and Bcl-2 messenger RNA (mRNA), which are mitochondria-related small molecules, were evaluated using real-time reverse transcription polymerase chain reaction. We found that the expression of microRNA-146a-5p was significantly lower (p < 0.01) and that of Bcl-2 mRNA was significantly higher (p < 0.01) compared to the control group (with no specific type of breast cancer). Conclusions: The significant changes in the expression of microRNA-146a-5p and Bcl-2 are specific to oncocytic carcinoma of the breast. Therefore, we suggest that the use of microRNA-146a-5p to target Bcl-2 has a potential therapeutic effect on oncocytic carcinoma of the breast.