Not all cancer is hereditary, but genetic experts are beginning to see a pattern in some cancers.
Everyone has two copies of each gene, one from each parent.
Each cell contains these copies, which during the development phases, tells them what to become, for example, a skin cell or a muscle cell. When changes, called Mutations, occur, this can lead certain cells to grow out of control.
These Mutations occur when a part of the gene is damaged and cannot be repaired. The medical term for the damaged cells is "abnormal cells". These cells then multiply themselves and don't die. Mutation has to occur in both cells to cause cancer. In Hereditary cancer, the person has inherited the damage from one of their parents. The damage could come from either one.
If the one gene is already damaged due to inheritance, this causes the person to be at high risk of developing cancer. It also changes the factors, and may cause the person to have a shorter time or skip a few stages once they had been diagnosed with cancer. The medical community uses the term "genetic susceptibility" in patients who have hereditary cancer.
Just because you have damaged genes doesn't mean that it is definite that you will be diagnosed with cancer. There have been cases of people who go through their whole life without ever receiving the bad news. Cancer patients who have hereditary cancer tend to get diagnosed earlier in life then those with sporadic cancer.
Sporadic cancer occurs when there is no history of cancer in the family. When looking at family history for cases of patterns, genetic specialists like to examine the last three generations. Of course, the further away the person is, the less chances are of you receiving the genetic, ie: your mother would be more of a concern then your great grandmother.
10% to 15% of cancers are hereditary for the following: breast, ovarian, and colorectal. The two genetics that are specifically checked are the BRCA1 and the BRCA2. These two account for 85% of all hereditary breast and ovarian cancers. 5% to 10% of all breast cancers are hereditary as well.
Not all cancers have anything to do with heredity. Cervical cancer is caused by a virus that is an STD. Other cancers like lung, pancreas and prostate also don't link up with heredity as strongly. If cancer does have a tendency to run in your family, it is best to have regular check ups and discuss how to lower the risks.