p53, Cytokeratin 19 Expression in Oral Squamous Cell Carcinoma and Correlation with Histopathologic Grading: An Immunohistochemical Study

The purpose of this study was to examine the immunohistochemical expression of p53 and cytokeratin 19 (CK19) in normal oral mucosa (NOM) and oral squamous cell carcinoma (OSCC) and their association with histopathological differentiation grade. The secondary goal was to see if there was any correlation between p53 and CK19 expression in NOM and OSCC. A hospital-based retrospective analysis was conducted in which 40 NOM and 45 OSCC samples were acquired from archives and stained with mouse monoclonal antibodies p53 and CK19. For both the NOM and OSCC groups, the proportion of positively stained cells, staining intensity, and staining index were calculated. p53 immunoexpression revealed that 85% of positively stained cells in the NOM basal layer had a low staining index (mean ± SD 1.87 ± 0.34), whereas 66.7% of positively stained cells in the OSCC had a high staining index (mean ± SD 5.63 ± 3.02). When NOM and OSCC were compared, there was a statistically significant difference in staining intensity. However, despite a linear increase in the percentage of positive cells from well to poorly differentiated, the comparison between histopathological grades was non-significant. CK19 exhibited 18.5% positively stained cells in the NOM basal layer with a low staining index (mean ± SD 1.57 ± 0.53), whereas OSCC samples showed 4.44% immunopositivity with a high staining index. p53 is a marker of oral carcinogenesis independent of histological grade and CK19 expression. Further, CK19 is a marker of dysfunctional epithelial differentiation but lacks sensitivity and specificity; however, it demands further multicentric studies with a large sample size to draw definitive conclusions.