CXCR4 and head and neck squamous cell carcinoma: Numerous markers, such as cytokeratin 19 (CK19), cytokeratin 8 (CK8), beta 2-microglobulin, cluster of differentiation (CD) 44, CD80, p53, C-X-C chemokine receptor type 4 (CXCR4), CC chemokine receptor 7, p16, pRb, human papillomavirus deoxyribonucleic acid (HPV DNA), and E6/7 viral genes, play an important role in predicting the metastasis and prognosis in head and neck squamous cell carcinoma (HNSCC) patients [3].