Involution of breast tissue and mammographic density.

Gertraud Maskarinec,Brenda Y Hernandez,Dan Ju,Lenora W M Loo,David Horio

doi:10.1186/s13058-016-0792-3

Gertraud Maskarinec, Brenda Y Hernandez + Show 3 more

Open Access

https://doi.org/10.1186/s13058-016-0792-3

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Abstract

BackgroundMammographic density decreases and involution of breast tissue increases with age; both are thought to be risk factors for breast cancer. The current study investigated the relationship between involution or hormone treatment (HT) and breast density among multiethnic patients with breast cancer in Hawaii.MethodsPatients with breast cancer cases were recruited from a nested case-control study within the Multiethnic Cohort. HT use was self-reported at cohort entry and at the time of the density study. Mammographic density and involution in adjacent non-tumor breast tissue were assessed using established methods. Linear regression was applied to evaluate the correlation between involution and four density measures and to compute adjusted means by involution status while adjusting for confounders.ResultsIn the 173 patients with breast cancer, mean percent breast density was 41.2% in mammograms taken approximately 1 year before diagnosis. The respective proportions of women with no, partial, and complete involution were 18.5, 51.4, and 30.1%, respectively and the adjusted density values for these categories were 32.5, 39.2, and 40.2% (p = 0.15). In contrast, the size of the dense area was significantly associated with involution (p = 0.001); the values ranged from 29.7 cm2 for no involution to 48.0 cm2 for complete involution. The size of the total breast area but not of the non-dense areas was also larger with progressive involution. Percent density and dense area were significantly higher in women with combined HT use.ConclusionsContrary to previous reports, greater lobular involution was not related to lower mammographic density but to higher dense area. Possibly, percent density during the involution process depends on the timing of mammographic density assessment, as epithelial tissue is first replaced with radiographically dense stromal tissue and only later with fat.

Highlights

Mammographic density decreases and involution of breast tissue increases with age; both are thought to be risk factors for breast cancer
Study population The current pathologic investigation [13] is based on Hawaii participants of the Multiethnic Cohort (MEC), who took part in a nested case-control (NCC) study of mammographic density and breast cancer risk [14]
Involution was not associated with percent density in premenopausal or postmenopausal women (p = 0.27 and 0.42, respectively), whereas the dense area remained higher with progressive involution (p = 0.04 and 0.02, respectively)

Summary

Introduction

Mammographic density decreases and involution of breast tissue increases with age; both are thought to be risk factors for breast cancer. The progressive replacement of glandular elements with collagen and fat is accompanied by histologic loss of epithelial cells available for malignant transformation and results in lobules characterized by acinar epithelia and fibrosis of the intralobular stroma [2, 3]. Delayed involution [2], i.e., variations in the rate or extent of decrease in the number and size of breast lobules with aging contributes to breast cancer risk [4]. Involution of the glandular structures of the breast may be reflected in mammographic density, an independent predictor of breast cancer. Biological processes underlying breast involution and density may share common hormonal influences, such as hormone therapy (HT), which affects breast cancer risk, involution, and mammographic density [10, 11]

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