Carcinoma of tongue and the buccal mucosa represent different biological subentities of the oral carcinoma

Purpose: Clinico-epidemiological studies show that the behaviour of the tongue cancer is different from the cancer originating at other sites of the oral cavity. However, studies identifying the reason for such difference are lacking in the literature. Methods: In the present study, we have attempted to see whether any difference existed in the cell cycle regulatory mechanism of these tumours by comparing immunohistochemically the expression of major cell cycle regulatory proteins in 147 buccal and 94 tongue carcinoma (anterior two-third of tongue) prospectively. Results: On comparison of buccal and tongue carcinoma, expression of p16 and p21 showed significant difference. In combined analysis, simultaneous down regulation of p16 and p21 was seen in 47% of tongue cancer cases as against 28% in buccal carcinoma (P=0.004). In univariate analysis, none of the clinico-biological variables studied showed significant association with survival in tongue carcinoma, whereas, some of the clinico-biological variables associated with survival in buccal carcinoma. Among the biological markers, the overexpression of cyclin D1 (P=0.007) and p53, detected using both the clones of antibodies—DO7 (P=0.008) and PAb240 (P=0.014) and the down regulation of p16 (0.033), showed significant association with shorter disease free survival (DFS) in these cases. Whereas in the case of overall survival (OS), overexpression of p53 [DO7 (P=0.031) and PAb240 (P=0.017)] and cyclin D1 (P=0.001) associated with poor survival. In multivariate analysis, the expression pattern of p53 and p16 protein influences the DFS whereas cyclin D1 expression showed independent association with the OS in buccal carcinoma. Conclusions: Thus, tongue and buccal cancers represent different biological subentities, and such differences should be considered in oral cancer management.