NBN and ductal breast carcinoma in situ: We analyzed the frequencies of 8 founder alleles in four genes including CHEK2 (c.1100delC, c.444 + 1G > A, del5395 and c.470T > C), PALB2 (c.509_510delGA and c.172_175delTTGT), NBN (c.657_661delACAAA) and RECQL (c.1667_1667 + 3delAGTA) among 564 Polish women with DCIS and compared with mutation frequencies in Polish cancer-free controls (4000 to 4702 controls for different variants).