GRIN2B and ductal breast carcinoma in situ: Aberrant promoter CpG islands hypermethylation of GRIN2B (NR2B coding gene) during breast cancer progression was reported, showing higher methylation levels and frequencies in ductal carcinoma in situ when compared with preinvasive lesions such as flat epithelial atypia or atypical ductal hyperplasia; significantly higher methylation frequencies in grade III than in grade I of invasive ductal carcinoma have also been shown which suggests that CpG island methylation of GRIN2B might be an early event in breast cancer progression (Park et al. 2011).