In general, cancer is not hereditary. There are only a few rare cases that are inherited, such as retinoblastoma, a type of eye cancer that occurs in children. However, there are some genetic factors that make certain people more sensitive to the action of environmental agents that cause cancer, which explains why some of them develop cancer and others do not, when exposed to the same carcinogen. 

All cancers are caused by changes in genes. Genes tell our body's cells which proteins to use for each cell type and their needs. Some genes tell the body how to correct the damage accumulated over time during normal aging, such as environmental toxins, exposure to the sun, dietary factors, hormones and other influences. These damage control genes can repair cells or tell cells when to stop growing and die if there is too much damage to repair. When genes are damaged, changes called mutations can appear. When these mutations occur in the genes, cells can grow out of control causing cancer. For most people who develop cancer, genetic mutations happen throughout life. Some people are born with a genetic mutation inherited from a parent, which increases their risk of cancer. When cancer occurs due to an inherited mutation, it is called hereditary cancer. 

Everyone has two copies of each gene, one from each parent. Most people are born with two normal copies of each gene. Hereditary cancers occur when a person is born with changes or mutations in a copy of a damage control gene that normally protects against cancer, usually these changes are inherited from the mother or father. People with an inherited genetic disorder have a

50% chance of passing the mutation to each of their children. These changes may increase the risk of cancer, but they do not increase the risk for each type of cancer, and not everyone who is born with a change in a gene will develop the disease. The scientific community uses the term genetic susceptibility to describe the increased risk for cancer in people with an inherited mutation. 

Hereditary cancer syndrome describes a mutation in the inherited gene that increases the risk for one or more types of cancer. The main inherited syndrome for breast and ovarian cancer is caused by mutations in the BRCA1 or BRCA2 gene, which substantially increases the risk of breast and ovarian cancer and will slightly increase the risk of other types of cancer. Signs of an inherited breast-ovarian cancer syndrome, which are not limited to any member of the family, include: 

● Ovarian cancer or fallopian tubes at any age. 

● Breast cancer before age 50. 

● Breast cancer in both breasts at any age. 

● Breast and ovarian cancer. 

● Breast cancer in men. 

● Triple-negative breast cancer 

Changes in BRCA1 and BRCA2 are more closely associated with an increased risk for breast cancer and ovarian cancer. Other neoplastic syndromes can increase the risk of breast or ovarian cancer. Hereditary colorectal cancer without polyposis, for instance, is a hereditary syndrome that can increase the risk for the following types of cancer: 

● Colon (mainly before age 50).

● Ovary. 

● Endometrium. 

● Stomach. 

● Small intestine. 

● Bile duct. 

Other hereditary mutations have been identified that do not increase the risk of breast or ovarian cancer, but increase the risk of other types of cancer. Any family with several people with the same type of cancer, diagnosed with cancer in young people or with rare types of cancer should consult a geneticist or onco geneticist to determine whether cancer in the family can be hereditary. In addition, there are families with multiple cases of breast cancer and/or ovarian cancer in which the mutation has not been identified. These familial cancers may have a hereditary component, but the genetic cause has yet to be identified. 

References: 

https://www.cancer.org/cancer/cancer-causes/genetics/family-cancer-syndromes.htmlhttps://utswmed.org/conditions-treatments/genetics-and-hereditary-cancers/hereditary-cancer-syndromes/