Some companies treat even the slightest dishonesty with termination.
With all due respect, from a new poster to a senior member, I strongly disagree with this statement. To the best of my knowledge, it is a violation of federal law for an employer to disregard your privacy and demand to know the details of your medical choices.
We all know that, 99% of the time, insurance companies will not cover surgery for gynecomastia. It's considered to be elective, meaning that the person having the surgery will have to pay for it out of their own pocket. That means that, since it doesn't involve the insurance company, it's of no concern to your company.
As I see it, you have one of two options:
1. You can take a vacation to coincide with your surgery. Personally, I get three weeks each year, with the choice of dividing it up into three blocks or taking it all at once. When I go for my surgery, I plan on taking a minimum of two weeks, possibly three. This will ensure that I get as much recovery time as possible, before returning to work.
2. Take some sick time. This second one would be harder, considering that your lost time will need to be documented with your work, whereas the vacation scenario wouldn't.
It's important to keep in mind that, regardless of which option you choose, you can always enlist the help of your PRIMARY physician, not your plastic surgeon. People need to realize that whenever they're having something medically done, their primary physician is ALWAYS involved! He or she receives (or should receive---you may need to make sure that it's being done) reports from the treating physician (in this case, the plastic surgeon) as to what has been done, what medications were prescribed, and any follow-up appointments. All of this goes into your file at the primary physician's office, so he or she can be kept informed and have the info at their disposal.
Why do I bring this up? Because your PRIMARY physician can write a work excuse for you, no questions asked! It completely negates the need to bring documentation from a plastic surgeon to your workplace, all the while ensuring that you have the protection of a medical excuse, something that may be needed if you have a job requiring any lifting, like thejuice mentioned.
I'm not sure how it is for others, but every physician I've ever spoken to for a work excuse has always worded it to MY desires, as long as it wasn't a flat-out lie. I'm sure that your primary physician would have no problem writing up a work excuse that would protect your privacy. Technically, all a physician is required to put down is that you were under his or her care and that some restrictions (if any) apply. That's it!
Myself, I believe that the benign growth route would be the best. It would adequately explain the vest and aftercare you'd be required to do following the surgery, all the while avoiding prying questions from concerned co-workers.
Remember: your workplace does NOT have the right to pry for details over any of your medical situations, ESPECIALLY if it has nothing to do with your work-provided medical insurance...