US scientists are developing a test that dentists could use to check if patients have breast cancer.
The test analyses proteins in spit
The test checks saliva for marker proteins that give an early warning of the disease.
Clinical trials of a prototype are in the planning stage, the University of Texas Dental Branch team told the journal Cancer Investigation.
The scientists are also investigating the use of saliva to spot other cancers, including cervical cancer.
They see the tests being used alongside existing detection tools, such as mammograms, ultrasound and tissue sample analysis.
They analysed saliva samples from 30 patients and found 49 proteins that differentiated those who were healthy and who had breast cancer tumours.
Crucially, the proteins could also distinguish between tumours that were benign or malignant.
Professor Charles Streckfus, who led the research, said dentists were well placed to spot diseases other than dental caries.
"Most folks, especially women and children, visit the dental office way more often than they ever see the physician. Saliva is a non-invasive, quicker way for detection."
But UK experts said the test might be more appropriate for use by GPs.
Professor Damien Walmsley, scientific adviser at the British Dental Association, said: "Maybe one day it will be feasible to go to the dentist to be screened for a variety of disorders in the body, including breast cancer, though it's more likely that the test will be done in specialist centres or by your GP."
He said saliva had been used as a diagnostic tool for a whole range of diseases, including cancers.
Proof of principle
"In the case of breast cancer, saliva analysis has been used to monitor patient response to chemotherapy or surgical treatment of the disease.
"The mouth itself is a good indicator of an individual's overall health, and dentists already play an important role in diagnosing and detecting oral cancers," he added.
Henry Scowcroft, of Cancer Research UK said researchers around the world were trying to find out if early signs of the disease can be found in bodily fluids like blood and saliva.
"This paper is one of many early 'proof-of-principle' results that are published every year. But the research only looked at samples from a very small number of people.
"The technique might not prove reliable when more people are studied and there's no data on how effective it might be in practice. So there's a lot more work to be done to find out if this method could ever be used routinely."
Antonia Dean of Breast Cancer Care said women should be reassured that current diagnostic tests, including the NHS National Breast Screening Programme, are extremely effective in detecting breast cancers.