These are changes that are inherited from our parents, or that occur spontaneously in very early development of the foetus.
These changes to the genome don’t match the human reference genome that we use for a guide. They are often passed down through generations. They can affect the chances of developing cancer, for example changes in the BRCA1 and BRCA2 genes can lead to an increased risk of breast and ovarian cancers. We look for these changes if they are thought to be the cause of someone’s cancer. We can also look for these changes in patients who don’t have cancer – but only if they want us to. In this case these are called ‘additional findings’.