In Canada, they did studies on male breast cancer. Since males often do not have the hormonal or repdocutive risks one needs to look at genetics and their environemnt. The study by Dr. Palli found that those with a family history of BRCA1/2 germ line mutations who were exposed to chemicals had modifying risk for chemical exposure or PAH damage in a small group of subjects.
A Danish study found that men who were exposed to combustion by-products such as gasoline and combustion according to the Danish Natinal Registrty were put risk for breast cancer, as it did women. There should be further studies.
(My father owned an oil company and had trucks at home. Yet no males had BC, but there is only one brother alive at this writing.)