I have been introduced to genotypes data and have found some interesting driver mutations that were already discovered in cancer. However, I also have found a few mutations in some new genes. For one particular gene, I have found that mutation in almost 95% (n= 80) of cancer samples and not in controls. I was told that this could be somatic mutation, but I am finding it difficult to understand why it is somatic mutation. I would really appreciate if someone can clarify this riddle to me.