Genetic loci with predisposing mutations include: BRCA1/ BRCA2 (autosomal dominant, 50%–85% life time risk) (Risch et al., 2006), TP53 (Li-Fraumeni syndrome, 80%–90% life time risk) (Allain, 2008), CDH1 (60% life time risk and primarily lobular subtype), STK11 (Peutz-Jeghers syndrome, 50% risk), PTEN (Cowden syndrome with 20%–50% risk (Lindor et al., 2008); Lynch syndrome with 25% risk), PALB2 (partner and localiser to BRCA2, age-dependent risk), ATM, BRIP1, CHEK2 (all about 20% risk) and RAD51C/RAD51D (14%–20% risk). Here, BRCA2 is linked to Cowden disease.