β-Catenin and Cyclin D1 in Mucoepidermoid Carcinoma of Variable Histologic Grades

OBJECTIVE: To analyze the expression of beta-catenin and cyclin D1 in mucoepidermoid carcinoma (MEC) of variable histologic grades to establish a correlation between the expression of these proteins and the different histopathologic grades of this neoplasia. DESIGN: Immunohistochemical analysis of MEC. SETTING: Pathological Anatomy Service, Discipline of Oral Pathology, Department of Dentistry, Federal University of Rio Grande do Norte, Natal, Brazil. PATIENTS: Fifteen cases of MEC, graded and categorized according to criteria reported in the literature into 5 tumors with a low grade of malignancy, 4 with an intermediate grade, and 6 with a high grade. MAIN OUTCOME MEASURES: Labeling patterns of beta-catenin and cyclin D1. RESULTS: No significant difference in beta-catenin labeling patterns was observed between low- and intermediate-grade tumors or between low- and high-grade tumors (P = .60 and P = .06, respectively; Fisher exact test), despite a strong tendency toward a difference in the latter. In contrast, a significant difference was noted between intermediate- and high-grade tumors (P = .03). For cyclin D1, no labeling was observed in any high-grade cases, and only 3 cases showed overexpression of this protein. Comparison of the labeling patterns among the different histologic grades revealed no significant difference. CONCLUSIONS: The reduced expression of beta-catenin observed in all high-grade MECs is probably due to the loss of its adhesion function, which confers a greater invasive potential to these tumors. The overexpression of cyclin D1 observed in only 3 MEC cases suggests that this protein does not participate in the etiopathogenesis of these tumors, which implies that other genes are likely responsible.