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Review
. 2024 Sep 16;19(1):65.
doi: 10.1186/s13006-024-00672-7.

Association between breastfeeding, mammographic density, and breast cancer risk: a review

Dong-Man Ye #  1 , Xiaoru Bai #  1 , Shu Xu  1 , Ning Qu  1 , Nannan Zhao  1 , Yang Zheng  2 , Tao Yu #  3 , Huijian Wu #  4
Affiliations
Review

Association between breastfeeding, mammographic density, and breast cancer risk: a review

Dong-Man Ye et al. Int Breastfeed J. .

Abstract

Background: Mammographic density has been associated with breast cancer risk, and is modulated by established breast cancer risk factors, such as reproductive and hormonal history, as well as lifestyle. Recent epidemiological and biological findings underscore the recognized benefits of breastfeeding in reducing breast cancer risk, especially for aggressive subtypes. Current research exploring the association among mammographic density, breastfeeding, and breast cancer is sparse.

Main findings: Changes occur in the breasts during pregnancy in preparation for lactation, characterized by the proliferation of mammary gland tissues and the development of mammary alveoli. During lactation, the alveoli fill with milk, and subsequent weaning triggers the involution and remodeling of these tissues. Breastfeeding influences the breast microenvironment, potentially altering mammographic density. When breastfeeding is not initiated after birth, or is abruptly discontinued shortly after, the breast tissue undergoes forced and abrupt involution. Conversely, when breastfeeding is sustained over an extended period and concludes gradually, the breast tissue undergoes slow remodeling process known as gradual involution. Breast tissue undergoing abrupt involution displays denser stroma, altered collagen composition, heightened inflammation and proliferation, along with increased expression of estrogen receptor α (ERα) and progesterone receptor. Furthermore, elevated levels of pregnancy-associated plasma protein-A (PAPP-A) surpass those of its inhibitors during abrupt involution, enhancing insulin-like growth factor (IGF) signaling and collagen deposition. Prolactin and small molecules in breast milk may also modulate DNA methylation levels. Drawing insights from contemporary epidemiological and molecular biology studies, our review sheds light on how breastfeeding impacts mammographic density and explores its role in influencing breast cancer.

Conclusion: This review highlights a clear protective link between breastfeeding and reduced breast cancer risk via changes in mammographic density. Future research should investigate the effects of breastfeeding on mammographic density and breast cancer risk among various ethnic groups and elucidate the molecular mechanisms underlying these associations. Such comprehensive research will enhance our understanding and facilitate the development of targeted breast cancer prevention and treatment strategies.

Keywords: Breast cancer; Breastfeeding; Mammographic density; Risk factors.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
The risk factors associated with breast cancer. Note: The figure was drawn by using Figdraw
Fig. 2
Fig. 2
The images represent different categories of mammographic density: (A) almost entirely fatty; (B) scattered areas of fibroglandular density; (C) heterogeneously dense; (D) extremely dense. Source: Images courtesy of Cancer Hospital of Dalian University of Technology, Liaoning Cancer Hospital & Institute
Fig. 3
Fig. 3
The biological impact of lactation on mammographic density
Fig. 4
Fig. 4
The association between lactation, breast density and breast cancer
See this image and copyright information in PMC

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