[huckleberrywine]

My nipples have been large for years; really showed on cold days especially when I wore a sweater. My boss would always comment either "turkey's done" or "a bit nippley today". I kinda enjoyed it. I found that just smiling works.

[Veronika41]

Gynecomastia.

That's the obvious answer.   It worked for Robert Paulson.

Sure  Gynecomastia.  it always happen the question  at swiming pool with 
friends

[ChuckM]

Interact on this one if you would, let's say your a male who has grown breast you can't hide anymore under your work clothes, what do you say when confronted with why do you have boobs / bra lines

I've never had anyone notice or comment about my breasts that I didn't want to, but if I was ever approached as you suggest in your question, it depends on who's asking.  Generally if it was anyone other than family or friends, I'd probably just say, "Thanks for pointing that out, I hadn't noticed."  No need to feel defensive, or that you need to explain, just show them the inappropriateness of their question.

Best regards,
ChuckM