More research is needed into the link between smoking and the development of breast cancer in women over 50, US scientists said.
The call comes as a new study from the US National Cancer Institute in Bethesda, Maryland, found that women who smoked after menopause were 19% more likely to develop cancer.
DR Sarah Nyante said her study adds to the growing body of evidence of the association between smoking and increased breast cancer risk.
Previous studies have investigated this relationship, but questions remained regarding the extent to which other breast cancer risk factors, such as alcohol intake, might influence the results.
More work is now needed to understand the mechanisms behind the link between smoking and breast cancer in post-menopausal women.