Mammographic breast density and the risk of breast cancer: A systematic review and meta-analysis.

OBJECTIVES: Mammographic density is a well-defined risk factor for breast cancer and having extremely dense breast tissue is associated with a one-to six-fold increased risk of breast cancer. However, it is questioned whether this increased risk estimate is applicable to current breast density classification methods. Therefore, the aim of this study was to further investigate and clarify the association between mammographic density and breast cancer risk based on current literature. METHODS: Medline, Embase and Web of Science were systematically searched for articles published since 2013, that used BI-RADS lexicon 5th edition and incorporated data on digital mammography. Crude and maximally confounder-adjusted data were pooled in odds ratios (ORs) using random-effects models. Heterogeneity regarding breast cancer risks were investigated using I2 statistic, stratified and sensitivity analyses. RESULTS: Nine observational studies were included. Having extremely dense breast tissue (BI-RADS density D) resulted in a 2.11-fold (95% CI 1.84-2.42) increased breast cancer risk compared to having scattered dense breast tissue (BI-RADS density B). Sensitivity analysis showed that when only using data that had adjusted for age and BMI, the breast cancer risk was 1.83-fold (95% CI 1.52-2.21) increased. Both results were statistically significant and homogenous. CONCLUSIONS: Mammographic breast density BI-RADS D is associated with an approximately two-fold increased risk of breast cancer compared to having BI-RADS density B in general population women. This is a novel and lower risk estimate compared to previously reported and might be explained due to the use of digital mammography and BI-RADS lexicon 5th edition.

Rat thymus macrophages: an immunohistochemical study on fetal, neonatal and adult thymus.

The pre- and postnatal development of the macrophage population of rat thymus is investigated applying enzyme-histochemical and immunohistochemical techniques, both on tissue sections and cell suspensions. A set of three monoclonal antibodies (ED1, ED2 and ED3), each of which recognizes cells of the monocyte-macrophage lineage in the rat, enabled us to distinguish between macrophages in the various compartments of the thymus. The medulla is characterized by ED1-positive dendritic cells, the corticomedullary region comprises numerous monocyte-like ED1-positive macrophages and the cortex contains a particular subpopulation of branched ED2-positive macrophages. Both the medullary dendritic cells and the cortical branched cells show Ia-membrane staining. ED3-positive cells are only occasionally present. During fetal life ED1-positive monocyte-like macrophages and dendritic cells are present. Just after birth ED2-positive cortical macrophages start to develop. Their number increases strongly during the first week after birth. The role of the various subpopulations of thymic macrophages is discussed.