Circulating tumor cells can display epithelial, mesenchymal, or mixed phenotypes. This heterogeneity is partly related to epithelial-mesenchymal transition, a biological process studied in tumor invasion and metastasis.
A workflow that relies only on an epithelial marker may underrepresent cells with reduced epithelial-marker expression. Including mesenchymal-associated markers can broaden the phenotypes available for review.
Marker expression alone does not establish malignancy. Cell morphology, multiple staining signals, assay controls, and the patient's clinical information must be considered together.
Research continues to evaluate how specific CTC phenotypes relate to prognosis and treatment response across different cancer types.
