Breast cancer is the 2nd most common cancer worldwide after lung cancer and the first most common cancer among women. BRCA1, BRCA2, HER2, and IDH1 are important genes that play a prominent role in breast cancer. Understanding gene expression involves investigating various molecular pathways and metabolic processes. In this review, we have focused on the isocitrate dehydrogenase (IDH1) gene’s role in cancer progression, especially in breast cancer and glioma. IDH-mutant tumors can alter DNA methylation, influencing tumor progression and the microenvironment. Although IDH1 expression is reduced in breast cancer, its expression in metastatic breast cancer is higher compared to non-metastatic breast cancer. We also explained the prevalence of IDH1 in different grades and stages of breast cancer, highlighting its clinical implications for diagnosis, prognosis, and potential targeted therapies.