Are you saying that those of us who have breast cancer probably developed it in our teenage years?

Some current thinking on the process of breast cancer formation is that some of the initial genetic events (a process we call “initiation”) probably occur in this very young age range. Breast cancer takes years and decades to develop from the first genetic damage until there's something you can feel or see on a mammogram.

There's a great deal of debate. If a woman gets breast cancer in her 90s, how long did it take to progress? If you're in your 40s, it's a much shorter time frame, but you can't prove that either one began in childhood or teen years. We just don't know.

All breast cancers are different from one woman to the next, so the genetic pathway will also be different. Many of these very early genetic events and exposures to carcinogens we think can occur very, very early, potentially even in utero, in sensitive stem cells in the mammary glands.