Comparison of Histological and Proliferation Features of Canine Oral Squamous Cell Carcinoma Based on Intraoral Location: 36 Cases

Grade and labeling indices for immunohistochemical tumor proliferation markers Ki-67 and proliferating cell nuclear antigen (PCNA) were evaluated in 36 cases of canine oral squamous cell carcinoma (OSCC) based upon intraoral location. Grade was significantly associated with location (P = .035). Grade II tumors were most frequently diagnosed. Grade I tumors were identified in the gingiva and the buccal mucosa, and grade III tumors were seen in the gingiva and the tonsillar region. Animals with tumors arising from the tonsils and of the tongue tended to be older (P = .007), and those in the former group were more likely to have metastatic disease at the time of diagnosis (P = .001). Mean expression of PCNA and Ki-67 proliferation index (PI) for all tumors were 62.54% and 50.70%, respectively, and there was a statistical significant association between the 2 variables (R = .70; P < .001). Proliferation index was not associated with any of the intraoral locations evaluated, but higher PCNA PI was significantly associated with grade (P = .031). Ki-67 PI was significantly associated with lymph node metastasis at the time of diagnosis, especially for OSCC of gingival location (P = .028). The results obtained in this study are preliminary but clinically relevant, since they provide information that can explain differences in biologic behavior among intraoral locations and contribute to more accurate tumor staging to support the choice for different treatment strategies available for OSCC.