TREM2 and head and neck squamous cell carcinoma: In HNSCC myeloid cells, scATAC peak–gene links reveal accessible enhancers at SPP1/APOE–TREM2 and CIITA that track, respectively, with SPP1+ lipid-handling TAMs and antigen-presenting macrophages, while motif deviations for IRF/STAT, AP-1, C/EBPβ, PPAR/MAF and PU.1 align with polarization and CXCL8–CXCR1/2–neutrophil programs, with orthogonal evidence still required for causality (26–28).