LEOMINSTER, Mass. – Breast cancer is the most common cancer among women in the U.S., but a local teacher is sharing his story to raise awareness of the disease’s potential impact on men as well.

Arthur O’Leary, 65, is a physics teacher at Leominster High School, and his classes are still in session as he battles stage IV breast cancer. He was diagnosed roughly a year ago.

“I was doing my stretches, like I always do every morning, and it felt like an acorn, kind of right here,” O’Leary said, gesturing toward the left side of his chest. “Once they discovered it, everything went fast.”

O’Leary underwent a mastectomy last winter, and is still going through chemotherapy.

“The kids I had last year, they were seeing me have no hair or a short haircut, there was no hair at all from January,” O’Leary said. “But it’s finally coming back.”

He said while many men might find it shocking to get the diagnosis – the odds of which are about 1 in 726 – he was aware of this slight risk from former Massachusetts Sen. Edward Brooke’s diagnosis in 2002.

As a scout master, he’s required to get a physical every year, and as part of his new effort to raise awareness, he’s urging all men to do the same.

“You have to get a physical every year, but the average guy hates going to the doctor,” O’Leary said. “But you’ve got to do it every year. Get it checked, if there’s any suspicion, I’d say get it checked because it’s a possibility.”

His oncologist, Dr. Gwen Caffrey, said paying attention to those early warning signs could make a huge difference. Caffrey practices at the UMass Memorial Medical Center University Campus and the HealthAlliance-Clinton Hospital Fitchburg Campus.

“It's too rare a phenomenon to have every man try to have a mammogram with the small amount of breast tissue that they have, and that makes awareness that much more important,” Caffrey said.

She added men should be on the lookout for changes in their nipple, or a change in the skin on their chest all along either the breast or the armpit.

“That would be something that they would really need to bring to their health care providers attention,” Caffrey said.

O’Leary, meanwhile, is grateful to help spread awareness and for the people who have helped him along the way.

“If you have a positive attitude, it seems to help things, and the people here are great because I’d be out every three weeks and they’d cover for me and send the homework for the kids to do,” O’Leary said.

For more information on the risk factors for breast cancer, visit UMass Memorial Health’s website. More information on the disease among men is also highlighted by the National Breast Cancer Foundation.