PTGS2 and nasopharyngeal carcinoma: To further confirm the relevance of COX‐2 and metastasis in NPC, seven paired NPC sequential samples with primary site and distant metastasis site that include two lung metastasis (P5 and P6) and five cervical lymph‐node metastasis (P1, P2, P3, P4, and P7) were explored to examine the COX‐2 expression in CAF.