There are at least 4 key things that have to take place before you trigger cancer. Is she at 1 or 2 or 3????
It takes two things to trigger cancer. Initiation and promotion.
Initiation is a change in the underlying structure of the cell that in and of itself can cause cancer. Depending on they type of tissue, the latency period can be months or years.
Promotion is something that can speed up the development of cancer after the initiation has occurred. It does not cause cancer by itself.
The gene would be iniation. It can cause cancer in and of itself. Basically its a question of when rather than if.
Estrogen is a promotor. It does not appear to iniate cancer but will promote the development of cancer in breast cells that are iniated making that cancer appear sooner and grow faster.
Unfortunately, a young woman with the gene is now carrying cells that are iniated and promoted, the combination with will most likelihood of causing cancer.