HOXB9 and head and neck squamous cell carcinoma: Similar correlation was observed between the grade of immune infiltration and HOXB9 expression across different cancer types in TCGA database with the XCELL, CIBERSORT and CIBERSORT-ABS algorithms, and the results revealed a positive correlation between HOXB9 and infiltration of mast cells in HNSCC (Fig. 6).