There are at least two men in England who have her2 positive breast cancer. One of them had a hard time getting herceptin because his insurance company wouldn't pay
http://news.bbc.co.uk/1/hi/england/kent/4600182.stm. I don't think it was just because he was a man, because that company was notoriously tight-fisted over herceptin.
Wasn't there also a man, I think from West Virginia, a few months back who posted on this board with her2 positive breast cancer?
It doesn't seem to be that common in men, though.