Estrogen and bc

It puzzles me that estrogen is considered to feed cancer, and yet the majority of women dx'd with bc are over 50 (when women theoretically have less estrogen due to menopause), while far fewer women under 50 are diagnosed with bc.

I don't think it is because there simply are more women over 50 who are living than who are under 50, because there should be numerically far fewer women that are older than 50 since less would have survived that long than in the younger population under 50?

I know it supposedly takes years for bc to develop, which would contribute some to the aging of those diagnosed, and also that the more years that one has high levels of estrogen the more likely one is to have cancer. But if that is true then why are some very young women being diagnosed with cancer when they haven't had many years of producing estrogen?

I bet that if these young women with bc were tested to determine their hormonal levels/composition science might find something different about hormonal balance that correlates with the reason some older women are more prone to develop bc.

A.A.