The Heterogeneity and Function of Stromal Cells in the Tumor Microenvironment

The tumor microenvironment is a central determinant of cancer progression, metastatic spread, and therapeutic resistance. Once considered passive scaffolds, stromal cells are now recognized as heterogeneous, active regulators of tumor behavior. Recent single-cell and spatial multiomics studies have resolved functionally distinct stromal subtypes, each defined by characteristic molecular programs and spatial niches, with specialized roles in extracellular matrix remodeling, immune evasion, and angiogenesis. This review synthesizes evidence for bidirectional stromal-tumor cross-talk in which cytokine networks (e.g., transforming growth factor-beta, interleukin-6, and C-X-C motif chemokine ligand 12/C-X-C chemokine receptor 4) coordinate epithelial-mesenchymal transition, stemness, chemotaxis, and vascular remodeling. Building on these insights, this review also argues for subtype-specific biomarkers and multimodal therapeutic strategies to overcome stromal-mediated resistance. Integrating stromal heterogeneity into precision-oncology workflows through standardized, lineage-resolved profiling and real-time biomarker guidance will be essential for diagnostic refinement and personalized treatment.