Microplastics and mammary carcinogenesis: A review of in vitro and in vivo experimental evidence.

Microplastics have emerged as environmental contaminants of growing concern due to their potential impacts on human health. The mammary gland represents a biologically relevant target because of its hormonal sensitivity, lipid-rich composition, and dynamic cellular remodeling. This integrative review synthesized experimental evidence on the effects of micro- and nanoplastics on breast tissue and breast cancer biology. A literature search was conducted in PubMed, Scopus, Google Scholar, and CAPES databases following PRISMA guidelines, identifying 14 eligible studies involving detection in breast milk and breast tissue, as well as toxicological investigations in in vitro and in vivo models. Experimental evidence indicates that microplastics can be internalized by mammary epithelial and breast cancer cells, inducing oxidative stress, mitochondrial dysfunction, inflammatory signaling, and genomic instability. Exposure was also associated with altered gene and protein expression, disruption of cell cycle regulation, and modulation of signaling pathways involved in tumor progression. Animal studies further suggest potential effects on tumor growth, inflammatory microenvironments, and histopathological changes in mammary tissue. Overall, current findings provide mechanistic and hypothesis-generating evidence that microplastics may influence biological processes associated with breast carcinogenesis under specific experimental conditions. However, methodological heterogeneity remains a major limitation, highlighting the need for standardized and translational studies.