Absolute risk of cancers in BRCA1 or BRCA2 mutation. A number of genes are associated with HBOC. The most common of the known causes of HBOC are: * BRCA mutations: Harmful mutations in the BRCA1 and BRCA2 genes can produce very high rates of breast and<unk>  cancer, as well as increased rates of other cancers. Mutations in BRCA1 are associated with a 39-46% risk of<unk>  cancer and mutations in BRCA2 are associated with a 10-27% risk of<unk>  cancer. Other identified genes include: * MLH1, MSH2, MSH6, PMS2: mutations in genes that lead to Lynch<unk>  put individuals at risk for<unk>  cancer. * TP53: Mutations cause Li-Fraumeni<unk> . It produces particularly high rates of breast cancer among younger women with mutated genes, and despite being rare, 4% of women with breast cancer under age 30 have a mutation in this gene. * PTEN: Mutations cause Cowden<unk> , which produces hamartomas (benign polyps) in the colon, skin growths, and other clinical signs, as well as an increased risk for many cancers. * CDH1: Mutations are associated with lobular breast cancer and gastric cancer. * STK11: Mutations produce Peutz–Jeghers<unk> . It is extremely rare, and creates a predisposition to breast cancer, intestinal cancer, and pancreatic cancer. * CHEK2: Approximately one out of 40 northern Europeans have a mutation in this gene, making it a common mutation. It is also one of the most frequently mutated genes after BRCA among Hispanics in the United States. Considered a moderate-risk mutation, it may double or triple the carrier's lifetime risk of breast cancer, and also increase the risk of colon cancer and prostate cancer. * ATM: Mutations cause ataxia telangectasia; female carriers have approximately double the normal risk of developing breast cancer. * PALB2: Studies vary in their estimate of the risk from mutations in this gene and the frequency of mutations in this gene may be different among different populations. It may be moderate risk, or as high as BRCA2. Approximately 45% of HBOC cases involve unidentified genes, or multiple genes.
Hereditary breast–ovarian cancer syndrome
Estrogen insensitivity syndrome
Aromatase excess syndrome
Hereditary leiomyomatosis and renal cell cancer syndrome
Hereditary lobular breast cancer
Multiple endocrine neoplasia
Angelman syndrome
Multiple endocrine neoplasia type 1