It is more scary in some ways because there is less tissue there than in a woman, and the big thing in cancer surgery is getting "clean margins". They lose part of the chest wall. I think people are surprised to hear that it happens in men, but it does. Maybe its less scary because the loss of a breast means something different to men than to women, but maybe its more scary medically as men are not looking for lumps and aren't alarmed by it as a woman would be so it is detected later.
Just be as supportive as you can- most hospitals should be able to help him find a support group of other people going through cancer treatment. There is tons of cancer information online- there has to be a way to help him find other men dealing with the same illness.
This looks like a good link:
http://www.johnwnickfoundation.org/index.html