Circulating Tumor Cells Atlas – an open-access repository capturing tumor cells heterogeneity and their ecosystem

Liquid biopsy is increasingly used in precision medicine, highlighting the need for standardized, image-based reference resources for reproducible identification and characterization of circulating tumor cells (CTCs). We present CTC Atlas (www.CTCAtlas.org), an open-access, community-oriented platform providing a curated compendium of CTCs with diverse morphological and molecular features, alongside other circulating tumor-associated cell types, including cancer-associated fibroblasts, macrophages, endothelial cells, and imaging artifacts. The platform integrates high-quality microscopy images with matched omics data, enabling systematic annotation, reproducible analysis, and comparative studies of tumor-related cells across laboratories. CTC Atlas addresses the lack of standardized reference frameworks in liquid biopsy, supporting reproducible workflows and facilitating cross-study comparisons. By providing structured, accessible datasets, the platform advances the understanding of tumor cell heterogeneity and dissemination dynamics in circulation and lays the groundwork for improved clinical applications of CTC-based liquid biopsy.