Summary: Hereditary Breast and Ovarian Cancer syndrome (HBOC) is a cancer predisposition syndrome caused by carrying a BRCA1 or BRCA2 gene pathogenic variant (mutation).
By JAX Clinical Education | July 2026
Hereditary breast and ovarian cancer syndrome (HBOC) is an adult-onset, cancer predisposition syndrome. HBOC is characterized by a high risk of breast and ovarian cancers, and an increased risk of other cancers such as male breast cancer, prostate cancer, pancreatic cancer, and melanoma. Individuals with HBOC tend to develop cancer at an earlier age than the general population, and have higher risk for bilateral breast cancer, and a second primary tumor in a different tissue. HBOC is not associated with any unique physician exam findings.
Cancer Type | BRCA1 | BRCA2 | General Population |
Breast | 60-72% | 55-69% | 12.9% |
Male Breast* | up to 1.2% | 1.8-7.1% | 0.1% |
Ovarian | 39-58% | 13-29% | 1.6% |
Pancreatic | ≤5% | 5-10% | 1.6% |
Prostate** | 7-26% | 15-20% | 12% |
Melanoma | No increase | Increased | 0.1-2.6% |
* male breast cancer risk by age 70 **prostate cancer risks by age 65 Adapted from NCCN v.3.2026 |
About 5-10% of breast cancers and 10-15% of ovarian cancers can be attributed to HBOC. An estimated 1 in 333-500 individuals in the general population have a disease-causingBRCA1 or BRCA2 mutation. About 1 in 40 individuals of Ashkenazi Jewish ancestry carry a BRCA1 or BRCA2 mutation. Statistical algorithms are available to determine the likelihood of a BRCA1 or BRCA2 mutation based on personal and family history.
Identification of a pathogenic variant in BRCA1 or BRCA2 by genetic testing is sufficient for the diagnosis of HBOC (see Genetic Testing and Referral Criteria, below).
HBOC is caused by a pathogenic variant in the BRCA1 or BRCA2 gene. When functioning normally, these genes are thought to serve as “caretakers” of the genome, correcting sporadic DNA errors due to faulty cell division or environmental exposures. Individuals with a pathogenic variant in BRCA1 or BRCA2 accumulate more DNA damage that can lead to cancer.
HBOC is an autosomal dominant condition. First-degree relatives of aBRCA1 or BRCA2 carrier have a 50% chance of also carrying the pathogenic variant. Men and women are equally likely to inherit, and pass on, a pathogenic variant.
While rare, individuals with BRCA2 pathogenic variants should be aware that if they have a child with another person who is also a BRCA2 carrier, the child has a 25% chance of having Fanconi Anemia, characterized by bone marrow failure, physical abnormalities, organ defects, and an increased risk of certain hematological cancers. Recently, there have been a few case reports of Fanconi-like conditions in individuals who carry two BRCA1 pathogenic variants.
Germline molecular testing includes sequencing and deletion/duplication analysis of BRCA1 and BRCA2. Often these genes are analyzed as part of a larger multigene hereditary cancer panel. A significant number of people meeting criteria for testing of the BRCA1 and BRCA2 genes have a pathogenic variant in a different gene. In the past, individuals with Ashkenazi Jewish ancestry may have been tested for three pathogenic variants in BRCA1 and BRCA2 that commonly occur in that population; currently broader genetic testing is recommended.
Criteria have been developed to identify individuals who would most benefit from genetic testing, based on red flags in the personal and family cancer history. Meeting one or more of the criteria below warrants further risk assessment, genetic counseling and genetic testing as appropriate.
See the USPSTF and NCCN guidelines below for testing criteria.
Increased surveillance (clinical breast exam, mammogram, and MRI) and consideration of risk reducing interventions (such as chemoprevention and preventive mastectomy or oophorectomy) are recommended, as well as consideration of targeted therapeutics for affected patients. See the NCCN guidelines below.
There are other hereditary cancer syndromes that increase the risk for breast cancer, such as Cowden syndrome and Li-Fraumeni syndrome. The presentation of these syndromes in a family may overlap with that of HBOC, but can sometimes be distinguished based on characteristic features, such as physical exam findings. In addition, moderate risk genes and a number of common genetic susceptibility variants are thought to increase breast cancer risk to a lesser extent thanBRCA1 and BRCA2. There are likely other genes that contribute to breast and ovarian cancer which have not yet been identified.
American Society of Clinical Oncology (2021): Assessing & Managing Your Patient's Hereditary Cancer Risk
GeneReviews (2026): BRCA1- and BRCA2-Associated Hereditary Breast and Ovarian Cancer
National Cancer Institute (2025): Genetics of Breast and Gynecologic Cancers PDQ.
National Society of Genetic Counselors (2021): Risk Assessment and Genetic Counseling for Hereditary Breast and Ovarian Cancer Syndromes.
National Comprehensive Cancer Network (v.3.2026): Genetic/Familial High Risk Assessment: Breast, Ovarian, Pancreatic, and Prostate (free registration required for access).
U.S. Preventive Services Task Force (2019): BRCA-Related Cancer: Risk Assessment, Genetic Counseling, and Genetic Testing.
American College of Obstetricians & Gynecologists (2017): Practice Bulletin #182: Hereditary Breast and Ovarian Cancer Syndrome.
American College of Obstetricians and Gynecologists (2019): Committee Opinion #793: Hereditary Cancer Syndromes and Risk Assessment.
American Society of Clinical Oncology (2020): Management of Hereditary Breast Cancer: American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Guideline.
American Society of Clinical Oncology – Society of Surgical Oncology (2024): Germline Testing in Patients With Breast Cancer: ASCO-Society of Surgical Oncology Guideline.
All information in this resource is provided for educational purposes only.