Breast mammographic pattern: a concatenation of confounding and breast cancer risk factors.

A mammographic pattern of > 25% radiodensity is associated with increased risk for breast cancer. Mammographic pattern is influenced by age, body weight, reproductive factors, and race/ethnicity. The interaction among these factors in predicting breast radiographic pattern, and their association with the presence of histologic markers of increased risk of breast cancer, is poorly defined. To elucidate the relations among epidemiologic, radiographic, and histologic markers of breast cancer risk, the authors studied these factors in an unselected forensic autopsy series, accumulated between 1978 and 1983, of 486 women aged 15-98 years at death. Older age and/or postmenopausal status was the strongest predictor of radiolucent breast pattern. Obesity, defined as a Quetelet index (weight(kg)/height(m)2) of > 25, and large breast size were also highly significant predictors of breast radiolucency. Factors related to parity were not significant predictors of breast parenchymal pattern. Native American race was an independent predictor of breast radiolucency in this population. A dense parenchymal pattern was associated with increased prevalence of marked cystic change and the presence of duct epithelial hyperplasia in women under age 35. The results support the association of breast radiodensity with ethnic/racial, reproductive, and histologic factors predictive of cancer risk. However, this association is overshadowed by the effects of obesity and aging or menopause.