Hereditary breast–ovarian cancer syndromes are cancer syndromes that produce higher than normal levels of breast cancer, ovarian cancer and additional cancers in genetically related families. It accounts for 90% of the hereditary cancers. The hereditary factors may be proven or suspected to cause the pattern of breast and ovarian cancer occurrences in the family. The name HBOC may be misleading because it implies that this genetic susceptibility to cancer is mainly in women. In reality, all sexes have the same rates of gene mutations and HBOC can predispose to other cancers including prostate cancer and pancreatic cancer. For this reason, the term "King syndrome" has recently come into use. The new name references Mary-Claire King who identified the genes BRCA1 and BRCA2.
Causes
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 ovarian cancer, as well as increased rates of other cancers. Mutations in BRCA1 are associated with a 39-46% risk of ovarian cancer and mutations in BRCA2 are associated with a 10-27% risk of ovarian cancer.
Other identified genes include:
MLH1, MSH2, MSH6, PMS2: mutations in genes that lead to Lynch Syndromeput individuals at risk for ovarian cancer.
TP53: Mutations cause Li-Fraumeni syndrome. 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 syndrome, which produces hamartomas in the colon, skin growths, and other clinical signs, as well as an increased risk for many cancers.
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.
Prevention
People with BRCA1 and BRCA2 mutations are recommended to have a transvaginal ultrasound 1-2 times per year. Screening with CA-125 is also recommended. Prophylacticsalpingo-oophorectomy is recommended at age 35-40 for people with BRCA1 mutations and at age 40-45 for people with BRCA2 mutations.
