While most women are not aware of the fluid, the nonlactating breast does produce a small amount that can be collected and tested.

"Nipple aspirate fluid (NAF) contains cells and secreted proteins, such as PSA (prostate-specific antigen) from the breast ducts ? the site of most breast cancers," said Edward Sauter, MD, PhD, a lead researcher of NAF and assistant professor of surgery at Jefferson Medical College of Thomas Jefferson University in Philadelphia. PSA was previously thought to be produced only in the prostate gland but now is known to be made also by the breast and may be associated with breast cancer risk.

In the most recent report on this screening procedure, published in the December 1999 issue of the British Journal of Cancer, Dr. Sauter analyzed the fluid from women with breast cancer. Breasts with large tumors and breasts removed by mastectomy were more likely to have NAF with cancerous cells recognizable under the microscope, with large numbers of growing cells and with cells that had an abnormal amount of DNA. This study of mastectomy specimens was a first step that has already led to several other studies of NAF analysis.

"Only recently, because of Dr. Sauter?s work, has the technology been available to aspirate sufficient quantities of nipple aspirate fluid ? and to be able to do so in nearly all women," said Robert Smith, PhD, director of cancer screenings for the American Cancer Society (ACS). "The ability to easily and inexpensively obtain NAF means that additional research on a potentially useful screening and diagnostic tool can proceed more readily than would have been possible before the development of these new specimen collection techniques."

Currently, a variety of NAF studies are underway at Thomas Jefferson University under the direction of Dr. Sauter. These studies are testing this method of early detection of breast cancer in women without symptoms. Although the findings so far are promising, they are preliminary and need to be confirmed in larger clinical trials, according to Dr. Sauter. This new method does not replace standard screening procedures for breast cancer, he said.

For screening, the ACS recommends women age 40 and older have an annual mammogram, an annual clinical breast examination by a health care professional and perform monthly breast self-examination. Women ages 20 to 39 should have a clinical breast examination by a health care professional every three years and should perform monthly breast self-examination.

The ACS estimates 182,800 new cases of invasive breast cancer will be diagnosed in US women this year. About 40,800 women are expected to die of the disease, making it the second leading cause of cancer death among women in this country.