IDO1 and head and neck squamous cell carcinoma: This cluster is similar to a population described by Zhang et al. in inflammatory conditions, expressing genes such as IDO1 and GBP1, and stimulated by IFN-γ and TNF-α.[35] Additionally, we identified a cluster not previously described in HNSCC with characteristics of myeloid-derived suppressor cells (MDSCs), particularly characterized by high expression of inflammatory cytokines including IL1β, but negative for the macrophage markers SPP1 and CXCL9.