More recently, Seppala et al (2003) have found that the CHEK2 variant 1100delC, known to be associated with an increased risk of breast cancer, is also associated with an increased risk of prostate cancer, and Dong et al (2003) found that this and other missense variants in CHEK2 occurred at increased frequency in prostate cancer cases. This evidence concerns the gene CHEK2 and breast cancer.