Family history of breast cancer, mammographic features of breast tissue, and breast cancer risk.

I reexamined the relations of family history of breast cancer in first-degree relatives, mammographic features of breast tissue, and breast cancer risk, using data from three case-control studies. Subjects included 1,047 cases with newly diagnosed breast cancer and 2,329 controls. Family history of breast cancer showed only a weak relation to mammographic features. In addition, while family history and mammographic features were each related to breast cancer risk, associations of these two factors with risk appeared additive. In contrast to previous reports, these data suggest that, to a large extent, family history and mammographic features have independent effects on breast cancer development.