My 1st breast exam actually took place during a school physical when I was 17.
I entered the doctor office and was told to remove my tshirt, only keeping a bra and knickers as usual. He looked at my ears, teeth, etc, then asked me different questions, one being "do you practise self-exam of your breasts?". I was 17 so no. He asked if I knew why it was to be done, I did know, but I said no because I didn't want to talk about it.
He told me it was to prevent breast cancer and "I'll show you how to do it then, please take off your bra". I HATED being topless in front of him and his nurse, the last time that had happened in a school physical was when I was 11 but I had no choice so I did it.
He started examining each breast, all the time explaining what he was doing and teaching me how to do it "do it by pressing small circles, quarter by quarter, once lying down, once when you shower". He also told me to do it once a month, right after my period.
He ended it by squeezing my nipples, nobody had ever done that to me before, of course, and I thought it hurt.
Then he still did a quick abdominal exam and ended the whole thing by a quick peek inside my knickers. To this day, I wonder what the point was, I don't think it was to evaluate my Tanner stage or anything like that, as I very clearly looked like a woman already.