Two goals of breast cancer research are to detect breast cancer in its earliest stages and to predict who will get breast cancer before a tumor actually develops. Current screening tools for breast cancer include clinical breast examination and mammograms, as well as a detailed family history. But research recently published in the Journal of the National Cancer Institute (JNCI) suggests a new screening method that can detect changes in breast fluid cells. The method, called nipple aspiration fluid cytology, uses a modified breast pump to take fluid from the breast ducts. The fluid is then tested for the presence of hyperplasia and atypia, cellular changes that may be precursors to cancer.

About the study

Between 1972 and 1991, researchers at the University of California, San Francisco, collected breast duct fluid via nipple aspiration from two groups of non-pregnant, non-lactating women, who were free of breast cancer at the time. Breast fluid was collected from the first group of 4046 women between 1972 and 1981 and was tested for hyperplasia and atypia. In 1991, the researchers collected data on breast cancer incidence in this group of women. The women who had atypia or hyperplasia in their breast fluid were at higher risk of breast cancer than the women whose breasts yielded no fluid when pumped and the women whose breast fluid had only normal cells.

The second group of 3627 women was studied between 1981 and 1991. The researchers collected breast fluid samples from these women and again tested the fluid. In 1996, they collected data on breast cancer incidence in both groups via a questionnaire that was mailed to participants. Of the 7673 women included at the start of the two studies, researchers were able to gather information regarding 6904 women. Reports of breast cancer on the questionnaires were confirmed with the cancer registry or medical records. This study provided a first follow-up for the second group and an additional eight years of follow-up for the first group.

The findings

Using the data collected from both study groups, researchers compared the results of the breast fluid tests with the incidence of breast cancer. Women who had breast fluid with hyperplasia or atypia were twice as likely to develop breast cancer as women whose breasts did not yield any fluid when pumped. Women whose breast fluid was normal were 30% more likely to develop breast cancer than women from whom no breast fluid was obtained. The results also indicate cascading degrees of risk: women with atypia and hyperplasia were at higher risk than women with normal cells, and women with normal cells were at higher risk than women whose breasts yielded no breast fluid at all.

Can nipple aspiration fluid cytology really predict which women are at high risk for breast cancer?

At this point, we don't know. Detecting hyperplasia and atypia in breast fluid may identify women who should be followed closely and screened regularly for breast cancer. But what about the fact that women whose breasts did not yield fluid were at lower risk than women with normal breast fluid and women with hyperplasia and atypia? These results suggest that producing breast fluid upon nipple aspiration may itself be indicative of some level of breast cancer risk. Currently, researchers don't fully understand why this might be. Without an understanding of this relationship, a nipple aspiration test does not provide conclusive information regarding breast cancer risk for the majority of women in this study, who yielded either no breast fluid (2775 women) or normal breast fluid (2627 women).

These findings support the theory that breast fluid may be a good place to look for signs that a woman is at risk for breast cancer, just as the first study alone suggested. The advantage of nipple aspiration is that it is non-invasive, whereas other methods of obtaining a breast fluid sample are at least minimally invasive. The authors explain that breast fluid analysis opens the door to new possibilities for predicting breast cancer risk. For example, scientists may one day identify biochemical breast cancer markers in breast duct fluid that can be detected on further analysis.

How does this affect you?

The findings from this study suggest that nipple aspiration fluid cytology may be able to predict breast cancer risk before a tumor develops. This would be an improvement over clinical breast exam and mammography, which only detect tumors once they have formed and reached a certain size.

Will you have a nipple aspiration test next time you see your doctor for breast cancer screening? Not likely. In their editorial accompanying this article, independent reviewers Carol Fabian and Bruce Kimler, caution that more research is needed to understand the results of nipple aspiration tests and how they are associated with breast cancer risk.