Maybe a de novo?

I am the youngest of 7 siblings, none of them have ever had cancer and neither have any of their 16 children. I feel pretty certain I am a de novo. My father did pass away in February of Leukemia, so we can't test him (but he was 83 at the time). I was diagnosed two years ago with prostate cancer and thought a simple surgery was going to be all I needed. Two surgeries later and one clinical trial, and I am still fighting advanced prostate cancer. It had spread to my lymph nodes. I went to a very academic doctor a few months ago who wanted to do very detailed genetic testing due to the aggressiveness of my cancer and it being an old person's cancer on someone as young as me. I never dreamed they would find anything, let alone a mutation on my tp53 and a Li-Fraumeni diagnosis. We just tested both of our children and are waiting on those results.