TUESDAY, Oct. 4 (HealthDay News) -- New research shows that the few men who develop breast cancer tend to have more advanced cases than women and to be diagnosed at an older age.

But when statistics are adjusted for factors such as age, men with breast cancer are less likely to die from the disease than women are.

The findings shed light on a rare disease in men, one that researchers had earlier assumed was deadlier for males.

"Men can develop it and should be aware that they should seek care if a breast lump develops," said study co-author Dr. Mikael Hartman, an assistant professor at National University of Singapore.

About 2,140 men in the United States will develop breast cancer this year, according to an estimate from the American Cancer Society (ACS), and about 450 men will die from it. The ACS estimates that the lifetime risk that a man will develop breast cancer is one in 1,000, although the likelihood skyrockets to 5 percent to 10 percent if a man has a mutation in a gene known as BRCA2, noted Dr. Mahmoud El-Tamer, an attending surgeon at Memorial Sloan-Kettering Cancer Center who studies male breast cancer.

The same mutation greatly boosts the risk of breast cancer in women.

It's not clear why breast cancer is much less common in men. Women, of course, have much more breast tissue. But volume doesn't appear to affect the risk of breast cancer in women, since those with large breasts don't develop the disease more than those with small breasts, El-Tamer said.

Estrogen could be key, study co-author Hartman said, since it seems to fuel breast cancer and is almost entirely absent in men.

In the new study, which appears online Oct. 3 in the Journal of Clinical Oncology, researchers analyzed statistics on breast cancer in both sexes in Denmark, Finland, Switzerland, Norway, Singapore and Sweden over the past 40 years. The researchers found 459,846 cases of breast cancer in women and 2,665 in men.

Women were diagnosed at age 62 on average and men at age 70. Men with breast cancer were less likely to live for five years than women with the disease were, but the situation reversed when researchers adjusted their statistics so they wouldn't be thrown off by differences between the two groups in terms of age and other factors.

Hartman said it's not clear why men do better, but it may have something to do with how their bodies react to anti-hormone and chemotherapy treatments. (Removal of the breast is another treatment for men with breast cancer.)

Over time, the prospects for women with breast cancer have improved at a greater rate than those for men, he said.

El-Tamer said men should be aware of the possible risk of breast cancer and see a doctor if they notice a lump or changes involving the nipple, such as an ulceration, discharge or changes in the areola.

More information

For more about male breast cancer, try the U.S. National Library of Medicine.