Women who receive false-positive results on mammograms have an increased risk of developing breast cancer in the next 20 years, a study has found.

A mammogram result is false positive when the screening tests indicate an abnormality, but the patient does not have breast cancer.

The latest study, published in Jama Oncology, suggests that the link between these false alarms and future breast cancer risk is highest in women between 60 and 75 years old and those with low breast density.

Low breast density indicates that fat tissue in the breast is more than fibrous and glandular tissue. However, higher breast density is typically associated with higher breast cancer risk.

Researchers made the findings after evaluating a large population of around 497,343 women who took mammogram screenings at 18 to 24-month intervals. The participants were between 40 and 74 years.

Around 3% of the participants received a false positive result, meaning they were called back for further examination that confirmed they did not have cancer.

In the next 20 years, 11% of women who received false-positive tests developed breast cancer compared to 7% of women without a false-positive mammogram.

The findings suggest that women with false-positive results were at a 60% increased risk of developing breast cancer over the next two decades, with age and breast density playing a crucial role.

Among women with a false-positive mammogram, those with low breast density were nearly five times more at risk of developing breast cancer.

"The elevated risk was higher in women in the 60–75 age bracket than in the 40–49 age bracket and women with low rather than high mammographic density. The risk was also highest in the four to six years following a false positive result," said lead author Xinhe Mao, a postdoctoral researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institute in Sweden.

Getting a false-positive is common for women with dense breasts as it is often hard to identify abnormal tissue on their initial mammogram. However, when women with low breast density get positive mammograms and are recalled for follow-up tests, it could be because of a tiny tumor that was missed or when there is a "proliferative" breast condition, Mao explained.

Proliferative breast condition is not cancerous but makes the breast cells look abnormal. However, they are associated with a heightened risk of breast cancer.

"It's important to accentuate a long-term awareness of breast cancer in women who get false positive mammography results. It might be beneficial to draw up personal monitoring programs for these women with careful follow-ups over the years immediately following," Mao said.

"Radiology and breast cancer screening are currently in a phase of rapid development, partly thanks to the use of AI. Our published paper is part of the general efforts to achieve better screening results and increase the screening program uptake," said the study's last author, Professor Kamila Czene, of the Department of Medical Epidemiology and Biostatistics at Karolinska Institute.