We all have thousands of genes that provide the instructions for our bodies to function optimally.
All cancers begin when changes occur in our genes. A change in a gene that disrupts its function is called a ‘mutation’, a “gene fault” or a ‘pathogenic variant’. Cancer usually results from an accumulation of many mutations. Most of the time, those mutations are confined (at least initially) to genes in the cells of the organ or tissue where they started. We call these type of genetic mutations ‘somatic’. Somatic mutations are not inherited from our parents, and they are not passed down to our children. This is why the majority of cancers do not ‘run in families’.
A small number of people are born with a gene fault or mutation that increases their chance of developing certain types of cancer.
In these people, cancer can get a ‘head start’ because when the first mutation is inherited from a parent it is present in every cell of a person’s body. This does not mean that a person will develop cancer in every cell of their body. In fact, we know that even when people are born with these gene faults or mutations, it is not guaranteed that they will develop cancer, but they are at a higher chance of developing certain types of cancer, depending on which specific gene is involved.