Breast cancer affects millions of women each year, but breast cancer also can be diagnosed in men. Each year in the United States, about 2,400 cases of breast cancer are diagnosed in men, according to the Centers for Disease Control and Prevention. Roughly 270 men will be diagnosed with breast cancer this year in Canada, according to the Canadian Cancer Society. Macmillan Cancer Support says men have a small amount of breast tissue behind their nipples, where breast cancer potentially can develop. Breast tissue in boys and girls is the same until puberty, when girls start to develop more. Signs of male breast cancer include a lump or swelling in the breast, redness or flaky skin in the breast, irritation or dimpling of the skin around the nipple, nipple discharge, or pulling in or pain of the nipple, states the CDC.