Exploring chromosomal instability and clonal heterogeneity in breast cancer.

Chromosomal instability (CIN), characterized by fluctuations in chromosome number or structure within cells, stands out as a hallmark of cancer, enabling tumors to thrive in hostile conditions. CIN serves as a driver of genetic diversity, giving rise to clonal heterogeneity (CH). Emerging evidence points to a potential correlation between CIN, CH, and the prognosis of breast cancer (BC) patients, especially in tumors exhibiting overexpression of the human epidermal growth factor receptor 2 (HER2+). However, our understanding of the role of CIN in other subtypes of BC is limited. Furthermore, it remains unclear whether CIN levels above a certain threshold in BC tumors could adversely affect tumor growth, or if lower to moderate levels of CIN might be associated with a more favorable prognosis for BC patients compared to elevated levels. Elucidating these relationships could significantly influence risk assessment and the formulation of future therapeutic approaches targeting CIN in BC. This study aimed to assess CIN and CH in tumor tissue samples obtained from Colombian patients diagnosed with luminal A, luminal B, HER2+, or triple-negative BC, and compare them with established clinicopathological parameters. The findings of this study indicate that BC patients exhibit intermediate CIN, high CH, and stable aneuploidy. All these characteristics were found to be related to clinicopathological features. Our results suggest that the identification of CIN, CH, and aneuploidy could improve cancer risk stratification, which could help to clarify the prediction of clinical outcomes and guide personalized therapeutic strategies for patients with different BC subtypes.