Researchers hope that one day they will be able to predice a woman's breast cancer risk by assessing her breast milk.
A research team led by environmental toxicologist Kathleen Arcaro of the University of Massachusetts Amherst will be conducting a series of experiments to identify methylated genes that indicate potentially pre-cancerous changes in breast cells.
The test could show signs of elevated breast cancer risk in women at an earlier age than ever before.
Methylation pushes cells toward cancer development because they represent potential tumour sites.
Early detection of methylation in breast tissue is a key in preventing cancer.
Arcaro suggests that current detection techniques such as ductal lavage and nipple aspiration yield very few cells, only tens or hundreds rather than the millions available from collecting breastmilk.
Also, breastmilk contains what Arcaro calls "a survey of cells from all the glands in the breast".
This significantly extends the reach of the risk assessment to many more breast tissues than other methods.
Because breast cancer in young women is rare, Arcaro says, "the main advantage many women will get from our new test based on breast milk samples will be peace of mind."
However, those few who are at elevated risk will find it out "far, far earlier than ever before," and the early warning should allow them to choose treatment options.