It is known that postmenopausal women taking estrogen plus progestin in hormone replacement therapy experience both increased breast density and breast discomfort. The researchers sought to determine whether the discomfort was a signal for increased density. Using data from women enrolled in the Postmenopausal Estrogen/Progestin Interventions Mammographic Density study, they found that women with new-onset breast discomfort showed a 3.9 percent increase in breast density, compared with a 0.6 percent density increase in women who did not experience discomfort.
Women with dense tissue in more than 75 percent of the breast face four times the risk of developing breast cancer than do women who have little or no dense breast tissue. Thus, new-onset breast discomfort during hormone replacement therapy may indicate an increased risk for developing breast cancer.