CHEK2 and breast cancer: Furthermore, variants of CHEK2 (1100delC, IVS2 + 1G/A, del5395bp, and I157T), PALB2 (509_510delGA and 172_175delTTGT) and RECQL (c.1667_1667 + 3delAGTA) are also associated with breast cancer in the Polish population.