Primary-Tumor Transcriptomic Signatures Associated with Circulating Tumor Cells Status in Breast Cancer: From CTC-Negative Remodeling to CTC-Associated Metastatic Programs

Background/Objectives: Circulating tumor cells (CTCs) play a central role in metastasis by enabling tumor dissemination through the bloodstream. However, the molecular transition from CTC-negative (CTC−) to CTC-positive (CTC+) states and their associated systemic remodeling remain poorly understood.