A groundbreaking study published in Nature has revealed that some breast cells in healthy women without known disease exhibit chromosomal abnormalities commonly associated with invasive breast cancer. This discovery challenges long-held assumptions about the genetic origins of breast cancer, raises questions about early detection methods, and prompts a reevaluation of what defines "normal" tissues in the body.
Key Findings
Researchers from the University of Texas MD Anderson Cancer Center studied breast tissue samples from 49 healthy women undergoing breast reduction surgery. The team used advanced single-cell DNA sequencing to analyse 83,206 epithelial cells—cells that line the ducts and lobules of the breast and are known to be the origin of most breast cancers.
Presence of Aneuploid Cells
Every woman in the study had a small percentage (median: 3.19%) of aneuploid epithelial cells—cells with abnormal numbers of chromosomes—in their "normal" breast tissues.
Older women showed a higher accumulation of these chromosomal changes, suggesting age-related progression.
Similarities to Invasive Breast Cancer
A significant proportion (median: 82.22%) of the aneuploid cells exhibited chromosomal alterations similar to those found in invasive breast cancers.
Common abnormalities included extra copies of chromosome 1q and losses of chromosomes 10q, 16q, and 22q—regions linked to genes implicated in breast cancer.
Implications Beyond the Breast
Since epithelial cells are found in other organs, these findings may have broader implications for understanding cancer risks across different tissues.
Challenges to Early Detection
As molecular diagnostic tools and early detection techniques, such as biopsies, advance, these findings pose potential challenges. Aneuploid cells in normal breast tissue could be mistaken for cancerous cells, leading to false positives and unnecessary interventions.
“This discovery forces us to reconsider when cancer actually begins,” said Dr. Nicholas Navin, senior author and chair of Systems Biology at MD Anderson. “While these cells appear cancerous under genomic analysis, they are found in healthy women. This highlights the complexities of cancer diagnostics.”
Rethinking Cancer Risk
The study raises questions about what factors, if any, might cause these cells to progress to cancer. Spatial mapping of these aneuploid cells showed they were concentrated in ductal and lobular structures, which are often involved in breast cancer. Further research is required to determine whether these cells pose a genuine risk or are simply a byproduct of natural cellular variation over time.
“It’s a reminder that our bodies aren’t perfect,” Navin added. “While these cells might not mean everyone is walking around with precancer, it emphasises the need for larger studies to understand their significance.”
Broader Implications
This discovery could reshape how cancer research is conducted, not just for breast cancer but potentially for multiple cancer types. It underscores the need for caution when interpreting diagnostic results and highlights the importance of continued research into cellular behaviour in "normal" tissues.
By understanding the role of aneuploid cells, researchers hope to develop better strategies to distinguish between benign abnormalities and those that may progress to cancer, ensuring more accurate diagnostics and improved patient care.
References
University of Texas MD Anderson Cancer Center. Healthy women have cells that resemble breast cancer, study finds.
Lin Y, Wang J, Wang K, et al. Normal breast tissues harbor rare populations of aneuploid epithelial cells. Nature, 2024.
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