Spatial organization of the TNBC tumor microenvironment: multicellular niches, T-cell bottlenecks, and therapeutic opportunities

Triple-negative breast cancer (TNBC) lacks stable druggable targets, is highly aggressive, and exhibits marked heterogeneity; consequently, therapeutic variability is often determined not only by tumor cell–intrinsic states but also by the immune–stromal ecology of the tumor microenvironment (TME) and its modes of spatial organization. The TNBC TME is jointly shaped by adaptive and innate immune cells, fibroblasts and the extracellular matrix, the vascular–hypoxia–lymphatic axis, and neural components, whose tissue-scale co-localization and boundary architecture underlie distinct phenotypes such as immune activation, immune exclusion, and immune desert. Recent advances in single-cell sequencing, spatial transcriptomics, and multiplex imaging now enable in situ characterization of cellular composition, functional states, spatial positioning, and local interactions, thereby grounding complex multicellular crosstalk in observable microanatomical patterns. Focusing on recurrent constraints on T-cell entry, intratumoral positioning and productive contact, and the maintenance of effector function, this Review synthesizes the spatial heterogeneity of adaptive immunity and local immune organization, and delineates how myeloid programs and neutrophil extracellular trap (NET) formation, cancer-associated fibroblast (CAF) subsets and extracellular matrix (ECM) barriers, aberrant vasculature and hypoxia-linked metabolism, and the tumor–nerve signaling axis cooperatively shape immunosuppressive niches that drive progression and therapeutic resistance. We further summarize spatial neighborhoods/niches that are reproducibly identifiable across cohorts in TNBC (e.g. hypoxic niches, the stromal–myeloid axis formed by co-localized CA9+ CAFs and SPP1+ macrophages, and tertiary lymphoid structure (TLS)-associated immune-activated units) and discuss their associations with prognosis and therapeutic response.Conclusions: Finally, integrating progress in TME-targeting clinical studies with window-of-opportunity sampling paradigms, we propose incorporating spatial neighborhood features and interaction signatures into stratification and dynamic assessment, and developing combination strategies centered on relieving myeloid suppression, remodeling stromal barriers, and correcting vascular/metabolic niches, with the goal of improving precision prediction and durable benefit of immunotherapy in TNBC. Finally, integrating progress in TME-targeting clinical studies with window-of-opportunity sampling paradigms, we propose incorporating spatial neighborhood features and interaction signatures into stratification and dynamic assessment, and developing combination strategies centered on relieving myeloid suppression, remodeling stromal barriers, and correcting vascular/metabolic niches, with the goal of improving precision prediction and durable benefit of immunotherapy in TNBC.