There is an old saying in plastic surgery: "It's not how much you take out -- but how much you leave."
This couldn't be more true than in gynecomastia surgery. The goal for this surgery is to make a patient look normal for their size and body type. If you are skin and bones and have larger breasts, then the surgery should try to remove as much tissue (gland and fat) as possible to make your chest [i]consistent with the surrounding tissues of your body. On the other hand, if you are overweight, then surgery should be done to remove enough tissue to get you flat but not overdone so that your chest skin is paper thin and not consistent with the thicker surrounding areas of your body. This is known as surgical artistry -- it is the art of the operation as well as the science of the surgery.
As has been previously stated, if one were to err, it should be on the side of leaving a bit too much (one can always go back and have more tissue removed) than taking out too much (replacement of tissue is very difficult).
Remember, this is not a breast cancer operation in which every last cell of breast tissue MUST be removed. This is basically a contouring operation in which at least some normal breast tissue must be retained under the areola to prevent it from caving in. Please understand, in all men, the normal and natural anatomy is for there to be breast tissue under the areola -- not fat. This is true for all men, whether they have gynecomastia or not.
To answer the original question of this thread, sufficient amounts of both gland and fat should be removed to make your chest as smooth and contoured as possible and also to make it consistent with the surrounding areas of your body.
I would suggest you have a lengthy discussion with your surgeon ahead of time in order to make him aware of your desires for surgery. And by the same token, the surgeon is obliged to tell you what he thinks he can do for you and what his goals would be. It is imperative that both the patient and the surgeon have similar goals for surgery -- and this should be discussed before deciding to proceed. If there is no agreement, then perhaps another surgeon should be consulted.
And if you should consult with more than one surgeon and find that both of them disagree with you, then you should perhaps take another look at your own objectives for surgery and re-assess them -- sometimes the doctor is right.
Dr Jacobs