According to the National Cancer Institute, HBOC is defined as “An inherited disorder in which the risk of breast cancer (especially before the age of 50 years) and ovarian cancer is higher than normal.” Most cases of HBOC syndrome are caused by certain mutations in BRCA1 or BRCA2. People with HBOC syndrome may also have an increased risk of developing other types of cancer, including melanoma, pancreatic and prostate cancers. Here, BRCA1 is linked to breast cancer.