For about 1,000 Americans a year, breast cancer is not a woman's affliction. It is diagnosed in about 1,000 men each year--about 1% of all cases.
It happens because men have more in common with women than many of them suspect.
All human embryos begin as females. But if the sperm at conception had the male "Y" chromosome, the embryo is modified as it grows, gradually changing from female to male.
It is the reason males have undeveloped nipples and a smattering of breast tissue identical to a woman's. During the hormone chaos of puberty, boys may even develop small breasts, which typically disappear within 18 months, once hormone balance is restored.
According to J. Randolph Hecht, assistant professor of medicine at UCLA, who researches male breast cancer, the disase in men is exactly the same as that in women, including some rare forms.
As with women, men tend to contract the disease after age 50. It is diagnosed and treated using the same methods, and the survival rate is about the same. Having a close male relative with breast cancer counts the same as a female relative when assessing breast cancer risks.
"Older men tend to get enlargement of their breasts because of a change in hormone balance. That's not uncommon," Hecht says. "But if a man finds a lump in his breast, especially if it's just on one side, he needs to go to a doctor.
"Most of the time, cancer shows up as a firm mass below the nipple, and often there is ulceration and discharge from the nipple. It's right there and usually fairly easy for a surgeon to biopsy."
Researchers presume breast cancer in males is promoted by the same hereditary and environmental factors that cause the disease in women. "But it's all speculation because it's such a rare disease," Hecht says.