Not that common
Although it is rare, breast cancer can occur in men as well.
Men possess a small amount of nonfunctioning breast tissue that is concentrated in the area directly behind the nipple on the chest wall. In a recent large international population-based study, men represented 0.6% of all breast cancer patients. http://womenshealthbeverlyhills.com/womens-health-blog/male-breast-cancer-rox-center/.