How did this mutation get into my family?

Most changes (also called mutations) in genes that cause an increased risk for cancer are inherited from a parent. But sometimes a gene mutation can arise as a new (also called de novo) mutation that occurred while that person was developing as a fetus, or even in mom’s egg or dad’s sperm, that are usually random. There are two main types of gene mutations: germline mutations and somatic mutation.

Germline gene mutations are changes in genes that are in every cell of someone’s body. They were born with it, and as their cells kept dividing to keep their body going, every cell that got made had that same change in the same gene. Somatic gene changes are mutations that happen usually to one or a small group of cells that only affects a small part of the body.