The relation of mammographic features of the breast to breast cancer risk factors.

The authors evaluated the relation of breast cancer risk factors to the appearance of the breast on xeromammograms. Subjects were 1021 women without breast cancer whose first xeromammographic examination at one of two Boston, Massachusetts, area hospitals was done for a reason described as "baseline" or "routine." The principal mammographic features assessed were the percentage of the breast showing nodular densities and the percentage showing homogeneous density. The extent of nodular and homogeneous densities decreased as age increased. The amount of both types of density decreased with increase in the number of full-term pregnancies. The percentages of the breast showing nodular and homogeneous densities were slightly higher for premenopausal compared to postmenopausal women, and for women with a history of breast biopsy or aspiration compared to women without. Certain characteristics of observed relations between risk factors and mammographic features differed for the two types of densities.