A doctor exams mammograms, a special type of X-ray of the breasts, which is used to detect tumours as part of a regular cancer prevention medical check-up at a clinic in Nice, south eastern France January 4, 2008. REUTERS/Eric Gaillard

One of the most aggressive forms of breast cancer may originate in the cells lining the mammary ducts, which can be targeted in the fight against the disease, experts in Australia say.

Basal breast cancers account for 20 percent of all breast cancers and are among the most aggressive. They occur in women carrying mutations of the tumor-suppressing gene BRCA1 and have long been thought to originate in breast stem cells.

However, a research team led by Jane Visvader and Geoff Lindeman from The Walter and Eliza Hall Institute of Medical Research in Australia has found that the real culprits may instead be pre-cancerous cells lining the mammary ducts.

The finding opens the way for developing new drugs or therapies to treat this form of breast cancer, Lindeman said.

BRCA1 women have approximately a 65 percent lifetime chance of developing breast cancer. Following surgery, treatment options available to these women are often limited to chemotherapy and radiotherapy, so identifying new treatment and prevention strategies is a priority for us, he said in a statement.

Breast cancer is the most common type of cancer among women and one of the leading causes of their premature death.

In the study, the researchers compared normal, non-cancerous breast tissues taken from BRCA1 mutation carriers, women not carrying the mutant gene, and women without the mutant gene but who had a positive family history of the disease.

Tissues from women with the mutant gene had high numbers of pre-cancerous cells lining the mammary ducts, they found.

These pre-cancerous cells were also genetically more similar to basal breast tumor cells, they wrote in their paper, which was published in Nature Medicine.

They are clearly abnormal cells as they have aberrant growth properties and the population is enlarged in BRCA1 mutation carriers, said Visvader in an email to Reuters.

One way to prevent this cancer was to target these pre-cancerous mammary duct cells, she added.

Our gene profiling studies have revealed genes that could serve as possible tumor markers that can be used in breast cancer diagnosis -- and has helped to identify possible therapeutic targets to treat (and possibly prevent) basal breast tumors, Visvader said.

Future work in this area is likely to help the next generation of women.