PTGS2 and head and neck squamous cell carcinoma: Unlike TNM-staging, most studies did not find any significant correlations between cancer grade and immunoexpression of COX-2, including studies on OSCC [25,39,51,54,55,60,67,78,91], HPSCC [24,64], LSCC [16], MEC [70], TSCC [37,88], HNSCC [52,74,81,85], NPC [72,73], and glottic cancer [89].