Detection of Circulating Tumor Cells with an Epithelial-to-Mesenchymal Transition Phenotype.

Breast cancer remains a leading cause of cancer-related mortality, particularly due to its metastatic potential. Circulating tumor cells (CTCs) have emerged as critical players in metastasis, offering potential as prognostic and predictive markers. Among CTC populations, those undergoing epithelial-to-mesenchymal transition (EMT) exhibit enhanced invasiveness, motility, and resistance to therapy. EMT-CTCs, often associated with cancer stem cell-like traits, contribute significantly to tumor progression and treatment failure. However, their detection is challenging due to their heterogeneous nature and partial EMT states. This chapter explores advanced methodologies for detecting EMT-CTCs, their molecular characteristics, and their clinical relevance in breast cancer. Biomarkers such as TWIST1, vimentin, and PLS3 are highlighted for their roles in identifying EMT-CTCs and tracking their transition states. The prognostic implications of EMT-CTCs, particularly their correlation with poor outcomes and resistance to therapy, underscore their potential utility in personalized medicine. Further research into standardizing detection techniques and understanding the complex interplay between EMT-CTCs and the tumor microenvironment is essential for integrating these insights into clinical practice.