Diabetes may raise the risk of breast cancer in post-menopausal women, according to experts.
An international team examined 40 separate studies looking at the potential link between breast cancer and diabetes. These studies involved more than 56,000 women with breast cancer.
Being obese or overweight has been linked to both conditions. But cancer experts say there may be a direct connection between the two.
The researchers found that post-menopausal women with Type 2 diabetes had a 27 percent increased risk of breast cancer. But there was no link for pre-menopausal women or those with Type 1 diabetes.
Writing in the British Journal of Cancer, the researchers have suggested that a high body mass index (BMI), which is often associated with diabetes, may be an underlying contributing factor.
"We don't yet know the mechanisms behind why Type 2 diabetes might increase the risk of breast cancer," the BBC quoted Prof Peter Boyle, president of the International Prevention Research Institute, who led the study, as saying.
"On the one hand, it's thought that being overweight, often associated with Type 2 diabetes, and the effect this has on hormone activity may be partly responsible for the processes that lead to cancer growth.
"But it's also impossible to rule out that some factors related to diabetes may be involved in the process," he stated.
Martin Ledwick, head information nurse at Cancer Research UK, added "From this study, it's not clear whether there's a causal link between diabetes and the risk of breast cancer in post-menopausal women.
"But as we know that having a high BMI can contribute to an increased risk of both Type 2 diabetes and breast cancer, it makes sense for women to try and maintain a healthy weight," he noted.