High-penetrance PVs in TP53, PTEN, and STK11 genes, involved in Li–Fraumeni, Cowden, and Peutz–Jeghers syndromes, respectively, are known to confer a high risk of childhood and adult cancers, including BC, with lifetime risks ranging from 40 to 80% [134,135,136,137,138], although these estimates may be overestimated due to the rarity of the conditions. The gene discussed is TP53; the disease is breast cancer.