Considering the important role of GBP2 as a possible tumor suppressor gene and theincreasing importance of epigenetics in gene regulations and cancer management, GBP2expression in breast cancer tumors with different histo-clinical characteristics andfor the first time, its promoter methylation as a possible epigenetic factor thatregulates this gene expression, were studied in both plasma and tumors. The gene discussed is GBP2; the disease is cancer.