Indeed, S100A8 and S100A9 mRNA levels in poorly or undifferentiated HNSCC were significantly lower p = 0.0004 and p < 0.0001, respectively) than well or moderately differentiated tumors, which were indistinguishable from normal samples based on analysis of microarray data GSE6791 from the GEO database (Figure 7). This evidence concerns the gene S100A9 and head and neck squamous cell carcinoma.