Xenium‐based spatial transcriptomic analyses uncover prognosis‐associated heterogeneity in the tumor microenvironment ( <scp>TME</scp> ) of angioimmunoblastic T‐cell lymphoma ( <scp>AITL</scp> )

Angioimmunoblastic T-cell lymphoma (AITL) exemplifies a neoplasm characterized by prominent inflammatory infiltration and robust immune responses in the tumor microenvironment (TME). The pathophysiology of refractory/recurrent (RR) AITL remains poorly understood due to profound intratumoral heterogeneity and complex TME features, contributing to limited therapeutic efficacy. Using Xenium-based spatial transcriptomics on 10 clinical samples, we compared RR AITL with treatment-responsive [non-refractory/recurrent event in 3 years (NR)] cases to map the TME architecture. We identified a novel cluster of NEIL3+ (Nei Like DNA Glycosylase 3) T-follicular helper (Tfh) cells, which exhibited stem-like characteristics at the transcriptional level, featuring self-renewal and multilineage differentiation capacity, and were highly enriched in RR tumors. Furthermore, we found major differences in immune cell organization between NR and RR microenvironments: RR cases were dominated by B cells primed for adaptive immunity and myeloid cells driving angiogenesis, whereas NR cases exhibited a chemokine-mediated regulatory landscape. These findings provide comprehensive characterization of the TME ecosystem in AITL and reveal potential therapeutic targets for high-risk RR AITL patients. © 2026 The Pathological Society of Great Britain and Ireland.