The breast ductal system contains the glands that produce milk and naturally secretes a substance called "nipple aspirate fluid".
For the study, the researchers at Nasa's Jet Propulsion Laboratory, Pasadena, California, employed the same sequencing and analysis methods used for examining bacteria in spacecraft assembly rooms.
"We applied these planetary protection techniques in the first-ever study of microorganisms in human breast ductal fluid," said Parag Vaishampayan, scientist in biotechnology and planetary protection at JPL.
The researchers found differences between the ductal fluid bacteria found in women who have experienced breast cancer, and the bacteria present in those who have not.
The findings were published in the online journal Scientific Reports.
The research team found that the community of microorganisms in breast ductal fluid differed significantly between two groups - 23 healthy women and 25 women who had a history of breast cancer and had gone through treatment.
It was then analysed with next-generation genomic sequencing, which has also been used for examining bacteria in Nasa spacecraft assembly facilities.
For the study, Nasa scientists collaborated with cancer researchers from different institutions.
"Collaboration between JPL space technology experts and medical researchers will continue to propel groundbreaking discoveries," Vaishampayan, who earned in PhD from University of Pune in Maharashtra, said.
"This publication represents a success for JPL's Medical Engineering Forum Initiative, which focuses on applying Nasa technology for medical needs here on Earth," JPL's Leon Alkalai, who is spearheading the initiative said in a statement.
Though the study found a correlation between specific species of bacteria and women who have gone through breast cancer treatment, the cause of the bacterial population difference is unclear.
However, the new research findings set the stage for further study on the role microbes may play in causing or preventing breast cancer. They are in line with recent research studies that suggest microbes contribute to 16 percent or more of malignancies worldwide.