ESR1 and neoplasm: Nonrandom distribution of methylation in tumor-related genes has previously been reported; Nass and coworkers [51] and Li and colleagues [45] found coincident methylation of CDH1 and ESR1, and Parrella and coworkers [52] reported that ESR1 promoter hypermethylation status correlates with those of CDH1, GSTP1, CCND2, and TRb1. Our findings revealed that occurrence of promoter region hypermethylation of RASSF1A, CCND2, GSPT1, TWIST, and APC are associated, whereas CDH1 methylation exhibited no correlation with methylation of those five genes (data not shown).