LEEDS, United Kingdom — Breast cancer is often thought of as a “woman’s” disease, in part because it remains one of the leading sources of female cancer mortality. But it’s not just women that suffer its ravages.

Indeed, for reasons that are still poorly understood, the incidence of male breast cancer is growing along with concern among oncologists that stigma and stereotypes about the disease may be preventing men from getting diagnosed early leaving them vulnerable to higher mortality rates than women.

A new study published in the journal Clinical Cancer Research highlights another important fact about gender and breast cancer: Because of basic biological differences as well as possible peculiarities in the etiology of male breast cancer, diagnostic and treatment methods developed for women may not be the best ones for men.

Researchers at the University of Leeds in England were able to identify two key proteins — known as eIF4E and eIF5 — that were present in male breast cancer patients who were less likely to survive the disease.

“We screened breast tumours from hundreds of men to find out if their tumours expressed these proteins, and we found that a significant proportion of the men we tested had higher levels of these proteins,” Matt Humphries, who helped direct the study, said in an article published in the online health magazine, Medical Xpress.

“These men were almost two and a half times more likely to die from their disease than those who had low levels of the proteins.”

Humphries noted that men with breast cancer are currently treated the same way women are – with mammograms and biopsies after a tumor is detected. But isolating the two proteins now gives oncologists a way to identify male breast cancer at a much earlier stage.

In some respects, male breast cancer is easier to detect because male breasts are typically smaller and a lump becomes more obvious earlier. However, it is also easier for a tumor to spreads to a man’s lymph nodes more quickly meaning that without early detection, men may not discovered their breast cancer until the disease is already fairly advanced.

Currently, breast cancer is not a leading cause of cancer mortality in men and the incidence rate among women is a thousand times higher. For example in 2016, there were roughly 2,300 new breast cancer cases for men, compared to 230,000 for women.

Some researchers believe increases in male incidence are due largely to diet and environmental factors, including consumption of unhealthy foods, alcoholism, and exposure to dangerous chemicals and other toxic influences at the workplace. While breast cancer incidence overall has slowed, male breast cancer incidence has grown 26% according to recent studies.

And in several African countries, including Uganda and Zambia, breast cancer incidence has skyrocketed to 5%-15% of the adult male population for reasons that are still poorly understood.

The University of Leeds study was funded by Yorkshire Cancer Research.

“It’s crucial that men are aware of the signs and symptoms of breast cancer so they are diagnosed at the earliest possible stage, but also that they are able to receive treatment that is tailored to their specific disease.” Kathryn Scott, the group’s interim director, said.