1. Department of Otorhinolaryngology Head and Neck Surgery, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
2. Department of Otorhinolaryngology Head and Neck Surgery, Xi'an Central Hospital, Xi'an, Shaanxi 710004, P.R. China
3. Department of Otorhinolaryngology Head and Neck Surgery, Xi'an Children's Hospital, Xi'an, Shaanxi 710003, P.R. China
4. Department of Pathology, Yanan University Affiliated Hospital, Yan'an, Shaanxi 716000, P.R. China