To assess the relationship between miR-21 expression and MIR21 methylation status, we analyzed eight major cancer types, including breast cancer (BRCA), LUAD, KIRC, bladder urothelial carcinoma (BLCA), LIHC, lung squamous cell carcinoma (LUSC), kidney renal papillary cell carcinoma (KIRP), and PAAD in TCGA data. The gene discussed is MIR21; the disease is invasive breast carcinoma.