Mutations can be divided to germline (~what you inherited, it's part of your normal dna, but it increases likelihood of getting cancer, for example by making d

Mutations can be divided to germline (~what you inherited, it's part of your normal dna, but it increases likelihood of getting cancer, for example by making dna self repair less effective, think Angelina Jolie) and somatic (random (?) mutations that enable unlimited growth, switch off cell death and so on and are only present in the tumor). There can be multiple mutation groups within a single tumor. Preemptive testing is useful and done for people with history of early cancers in family but obviously can detect only germline mutations. Most of the targeted therapies target somatic mutations. Some hospitals doing genomic testing share their data through AACR GENIE project https://www.aacr.org/Research/Research/Pages/aacr-project-genie.aspx https://www.aacr.org/Research/Research/Pages/aacr-project-ge...