ENPP2 and breast cancer: It is quite clear by recent findings that methylation of ENPP2 at the promoter region or 1st exon holds a significant role in the regulation of its expression, and it has been proposed that ENPP2 methylation can serve as a biomarker for BC diagnosis and prognosis with the potential to be implemented in liquid biopsy, i.e., detected in ccfDNA, baring additional clinical value.