TERT and breast cancer: In this study, we developed highly sensitive droplet digital PCR (ddPCR) assays for detecting low-allelic fraction TERT promoter mutations (C228T, C228A, CC242-243TT and C250T) in urinary cell-free and/or cell pellet DNA of BC patients and compared their performance with our previously established NGS-based assay (UroMuTERT) in two independent case-control studies: DIAGURO (n = 89 cases and n = 92 controls) and IPO-PORTO (n = 49 cases and n = 50 controls).