NTHL1 and neoplasm: To assess the occurrence of somatic bi-allelic inactivation in NTHL1 and characteristic mutational signatures in NTHL1-associated tumors, targeted sequencing was performed on tumor DNA from cases with a germline NTHL1 LoF variant using a custom-designed panel of 259 genes (total targeted region of 1.337 Mb) that included all exons and exon-intron boundaries of NTHL1 and 27 breast-cancer driver genes11.