I had to get a mammogram before top surgery because my surgeon requested it. But I was in my mid-forties, so my GP had been pressing me to get one anyway. (Little pun there.)
It was kind of horrible, but I was greatly relieved when it was over because I knew I would never have to go through it again.
Or so I thought. And then I received the results: I had some suspicious findings on one side, so I had to have a screening mammogram and an ultrasound. As far as I know, these and a clinical breast exam are the main diagnostic tools unless you actually have a lump or cyst or something else that is obviously suspicious. But I'm not a doctor; your best bet is to discuss your concerns with a physician you trust.
The practitioners expose you as little as possible, but they do touch you there. If you have to have such procedures and don't think you can get through them gracefully, ask about a sedative.
I also had a presurgical physical exam that involved heart, lungs, urinalysis, blood work, and so forth. I had to be partly exposed while he used the stethoscope, and he did briefly make contact there, but I dealt with it. He knew what the surgery was for, so maybe he was extra careful not to freak me out. I did not need a GYN visit to get top surgery.
