Ki‑67 is an independent prognostic marker for the recurrence and relapse of oral squamous cell carcinoma

As a nuclear and nucleolar protein, proliferation marker protein Ki‑67 (Ki‑67) serves a vital role in tumorigenesis due to its positive correlation with tumor proliferation. High expression of Ki‑67 in the cell cycle from the G1 to M phase makes it a potential biomarker for certain tumors and useful for selecting medical treatment. However, the diagnostic value of Ki‑67 in oral squamous cell carcinoma (OSCC) has not been fully evaluated. In the present study, the objective was the elucidation of the prognostic value of Ki‑67 in a large number of OSCC patients. Ki‑67 expression was detected by immunohistochemical staining methods in 298 OSCC specimens and 98 tumor‑free oral mucosa specimens (62 dysplasia mucosa and 36 normal mucosa), acquired from Nanjing Stomatological Hospital, Medical School of Nanjing University (Nanjing, China). Expression of Ki‑67 in normal tissues, dysplasia tissues and OSCC tissues was compared. Associations between Ki‑67 expression and clinicopathological parameters were analyzed by χ2 test. Kaplan‑Meier survival curves and Cox progression analysis were used to assess the diagnostic value of Ki‑67 for OSCC. The results showed that Ki‑67 expression was higher in OSCC tissues than in tumor‑free tissues and that it increased with the progression of dysplasia in oral mucosa tissues. In addition, patients with high Ki‑67 expression had a worse clinical outcome, including poor tumor differentiation (P=0.001), increased positive lymph node metastasis (P=0.006) and increased worst pattern of invasion type (P<0.0001). Kaplan‑Meier survival analysis demonstrated that higher Ki‑67 expression was associated with poorer overall survival (OS) (P=0.035), recurrence‑free survival (RFS) (P=0.017), metastasis‑free survival (MFS) (P=0.032) and disease‑free survival (DFS) (P=0.018) times. Additional multivariate analysis demonstrated that Ki‑67 expression was negatively associated with OS, DFS, RFS and MFS. In conclusion, Ki‑67 overexpression is associated with the progression of OSCC and serves as an independent prognostic factor for OSCC patients.