Evaluation of Ki-67 Labeling Index Across Histopathological Grades of Oral Squamous Cell Carcinoma

Abstract

Objective: Oral squamous cell carcinoma (OSCC) is one of the most common malignancies of the oral cavity and remains a major cause of morbidity and mortality, particularly in developing countries. Although histopathological grading is routinely used to assess tumor differentiation, it may not accurately reflect the biological behavior of the tumor. Ki-67, a nuclear proliferation-associated antigen, has emerged as a valuable biomarker for evaluating tumor proliferative activity and aggressiveness. The present study aimed to evaluate the Ki-67 proliferative index in oral squamous cell carcinoma and determine its correlation with histopathological grade. Methods: This cross-sectional observational study included 50 histopathologically confirmed cases of oral squamous cell carcinoma. Hematoxylin and eosin (H and E)-stained sections were graded according to Broders' classification. Immunohistochemical staining for Ki-67 was performed using the MIB-1 monoclonal antibody, and the Ki-67 labeling index (LI) was calculated as the percentage of positively stained tumor cell nuclei. Statistical analysis was performed using one-way analysis of variance (ANOVA) and Spearman's rank correlation test. A p-value of<0.05 was considered statistically significant. Results: Among the 50 cases included in the study, 72% were males, with the highest incidence observed in the sixth decade of life. The buccal mucosa was the most frequently affected site (86%). Histopathological examination revealed that 48% of tumors were well differentiated, 42% were moderately differentiated, and 10% were poorly differentiated. The mean Ki-67 labeling index increased progressively with tumor grade, measuring 10.0% in Grade I, 31.2% in Grade II, and 46.8% in Grade III tumors. This increase was statistically significant (p<0.001). A strong positive correlation was observed between Ki-67 expression and histopathological grade (Spearman's ρ = 0.670, p = 0.0001). Higher Ki-67 expression was predominantly associated with poorly differentiated tumors and tobacco exposure. Conclusion: Ki-67 expression demonstrates a significant positive correlation with histopathological grade in oral squamous cell carcinoma. The proliferative index increases with decreasing tumor differentiation, suggesting that Ki-67 is a valuable adjunctive biomarker for assessing tumor aggressiveness and improving prognostic evaluation in patients with OSCC.