How Cancer Develops
Cancer develops in two ways: sporadic cancer (does not run in the family) and inherited cancer (runs in the family).
How Sporadic Cancer Develops
Cancers that do not run in families are called sporadic cancers. Sporadic cancers happen by chance or by causes that are not passed on from parents to children in families.
Sporadic cancer can be caused by several factors. Some of these are:
- Harmful chemicals
- Radiation (for example, from the sun)
- Aging
Other cancers are said to be inherited, or passed on in families. A person can inherit a mutation that raises his or her risk for cancer.
- Sporadic cancer develops this way: Chromosomes are normal at birth
- In women with sporadic cancer, the first mutation can occur in the gene of a cell during her lifetime
- In women with sporadic cancer, the second mutation can occur in the gene's other copy in the same cell and a tumor may develop
- Sporadic cancer mutations happen because of errors in copying DNA when new cells are made. The risk of sporadic mutations increases with age.
How Inherited Cancer Develops
- First mutation is inherited and is found in all body cells
- Second mutation occurs during a person's lifetime and a tumor develops
There are three main differences between sporadic and inherited cancers.
Sporadic cancer is associated with:
- Single tumors
- One affected breast (if breast cancer)
- Later onset in life
Inherited cancer is associated with:
- More than one tumor
- Two affected breasts (if breast cancer)
- Earlier onset in life (for example, breast cancer at less than 50 years of age)