Histoscore and Discontinuity Score − A Novel Scoring System to Evaluate Immunohistochemical Expression of COX-2 and Type IV Collagen in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma

Introduction: Cyclooxygenase 2 (COX-2) expression in oral potentially malignant disorders (OPMDs) such as oral submucous fibrosis (OSMF) and oral squamous cell carcinomas (OSCCs) has revealed inconclusive reports. Studies on loss of type IV collagen expression in oral epithelial dysplasias (OEDs) and OSCCs were subjective and lacked systemic approach. To evaluate the immunohistochemical (IHC) expression of COX-2 and type IV collagen in OED, OSMF, and OSCC. Materials and methods: IHC expression of COX-2 and type IV collagen on paraffin-embedded tissue section of 10 cases each in normal oral mucosa, mild OED, moderate OED, and severe OED, OSMF, and OSCC were evaluated using mean H score and discontinuity Score (DS) designed grades for every group, respectively. Mean H score of COX-2 was compared within and between the groups using analysis of variance (ANOVA), and DS designed specifically for type IV collagen expression was compared using Kruskal–Wallis ANOVA. Pairwise comparison between the groups were performed using Tukey multiple posthoc procedure and Mann–Whitney U test for COX-2 and type IV collagen, respectively. Results: Mean H scores of COX-2 expression increased significantly (P = 0.0001) as disease progressed from mild OED to severe OED. But COX-2 in OSCC was less than that observed in mild OED (P = 0.0001). Expression of COX-2 in OSMF was more than that observed in moderate OED. Type IV collagen expression decreased as disease progressed from OED to malignancy (P = 0.0001). OSMF indicated a variation in grades of loss of type IV collagen expression. Conclusion: Expression of COX-2 in OED, OSMF, and OSCC and DS for type IV collagen expression in our study could be effectively applied to assess the malignant potential of OPMDs. However, further studies need to be implemented on a larger sample size to conclude the above findings.