High-penetrance breast cancer susceptibility gene mutations associated with inherited breast cancer syndromes, such as BRCA1, BRCA2, PTEN (Cowden’s syndrome), TP53 (Li Fraumeni syndrome), STK11 (Peutz-Jeghers syndrome), CDH1 (hereditary invasive lobular breast-diffuse gastric cancer) and those with an associated family history account for approximately 10% of breast cancers (84). The gene discussed is STK11; the disease is breast cancer.