In the journal Clinical Cancer Research, the team - from the Mayo Clinic in Rochester, MN - suggests that the findings reveal important clues about the role of the immune system in the early stages of breast cancer development.
First author Dr. Amy Degnim is a breast surgeon who specializes in the study of breast tissue for very early signs of premalignant change.
She says the new study supports the idea that immune-related approaches such as vaccines may be effective in preventing breast cancer.
Breast cancer is cancer that begins in the cells of the breast, although it can spread to other parts of the body. It can occur in both men and women, but it is rare in men.
In the United States, breast cancer is the second most common cancer in women after skin cancer.
Based on current incidence rates, a woman born in the U.S. today has a 1 in 8 chance of developing breast cancer during her lifetime.
Study used tissue from benign breast disease donors
For their case-controlled study, Dr. Degnim and colleagues quantified various types of immune cell in different types of breast tissue. They used samples of normal breast tissue from donors to the Susan G. Komen for the Cure Tissue Bank, and samples of breast tissue from women diagnosed with benign breast disease at the Mayo Clinic.
Fast facts about breast cancer
- A woman's risk of developing breast cancer rises with age
- In the U.S., 89.7 percent of women with breast cancer survive for more than 5 years after diagnosis
- In 2013, there were more than 3 million women living with breast cancer in the U.S.
Some noncancerous breast conditions may not present symptoms and may only be found during a mammogram. Sometimes, however, they can present in a similar way to breast cancer, so it can be hard to differentiate them from breast cancer just from symptoms alone.
Unlike breast cancers, benign breast diseases are not life-threatening, but some are connected with a higher risk of developing breast cancer later in life.
Some of the study participants with benign breast disease went on to develop breast cancer later.
Altogether, the researchers collected data on 94 age-matched triplets.
Each triplet comprised: a normal breast tissue case; a benign breast disease case in which the donor developed breast cancer later; and a benign breast disease case where the donor remained cancer-free.
'Immune system role in breast cancer development'
The results showed that the composition of immune cells in the breast tissue was different in the three different types of donor.
For example, compared with normal breast tissue, breast tissue from donors with benign breast disease had higher proportions of certain immune cells, particularly dendritic cells and macrophages. These types of immune cell work together to create an immune response.
The researchers also found that tissue from donors with benign breast disease who later developed breast cancer showed lower levels of B cells - a type of immune cell that produces antibodies.
They suggest that the reduced levels of B cells in breast tissue of women with benign breast disease who later develop cancer indicates that B cells may play an important role in preventing disease progression, and they may serve as a biomarker for breast cancer risk.
"Our findings provide evidence that the immune system may have an important role in promoting or inhibiting breast cancer development in its very earliest stages."
Dr. Amy Degnim