PTPRO and breast cancer: Similar to our previous data showing that PTPRO methylation correlates with advanced stage in esophageal squamous cell carcinoma[15], our clinicopathologic correlation analysis, showing that PTPRO promoter methylation correlates with tumor histological grade (P = 0.028) suggests that the PTPRO silencing influences breast cancer differentiation and more directly correlates with aggressive biological behaviour of tumor.