A virus that is usually considered harmless has been found to occur at an abnormally high rate in breast cancer tissue, reports CBS News Correspondent Elizabeth Kaledin.
The Epstein-Barr virus is so prevalent it has infected at least 90 percent of the world's population. Already a common cause of mononucleosis, now researchers have determined Epstein-Barr may also be linked to breast cancer.
In a study published in Wednesday's Journal of the National Cancer Institute, the virus was found in 51 out of 100 breast cancer tissue samples, and in the most aggressive tumors. Only three out of 30 healthy breast tissue samples contained the virus.
According to Dr. Clifford Hudis, of Memorial Sloan Kettering Cancer Institute, "Potentially, a virus might turn on some of the reproductive machinery of a cell, so that the cell grows in an unregulated or uncontrolled fashion."
But the study did not determine that Epstein-Barr virus can cause breast cancer, and Hudis believes that connection is far off. "There must be more to this story," he says. "If Epstein-Barr virus has any role in breast cancer, it may be as one of many co-factors."
On the whole, doctors say the discovery asks more than it answers. Now the most important question is: Could some breast cancers be caused by a virus, and if so, could the disease one day be prevented by a vaccine?
Microbiologist Dr. Robert Garry, of the Tulane Medical School, says the findings break new ground. Garry's own research has lead him to a virus that causes breast cancer 95 percent of the time in mice and 85 percent in a small number of human samples. He believes locating cancer-causing viruses is the next frontier in tackling the disease. "For many cancers, certainly targeting the virus is the next wave not only of detection, but perhaps prevention and therapy too," he says.
Meanwhile, until a stronger link can be made between breast cancer and any virus, doctors believe early detection and good treatment are still their best weapon.