ETAR/CXCR4 expression levels and their prognostic value in undifferentiated NPC. A-F. Immunohistochemical staining pattern of ETAR/CXCR4 expression. A. Positive staining for ETAR in prostate cancer tissue. B. Negative staining for ETAR in normal nasopharynx tissue. C. A case of negative staining for ETAR. D. A case showing strong (≥50%) cytoplasmic staining for ETAR. E. A case showing strong cytoplasmic staining for CXCR4. F. A case showing strong nuclear staining for CXCR4. Original magnification, × 200. G-N. Kaplan-Meier estimates of survival curves based on the ETAR/CXCR4 expression levels of all 153 patients. G-J. Based on the ETAR expression levels. G. Overall survival, P = 0.004. H. Progression-free survival, P = 0.001. I. Locoregional-relapse-free survival, P = 0.14. J. Distant-metastasis-free survival, P = 0.001. K-N. Based on the CXCR4 expression levels. K, Overall survival, P < 0.0001. L, Progression-free survival, P < 0.0001. M. Locoregional-relapse-free survival, P = 0.024. N. Distant-metastasis-free survival, P < 0.0001.