Pleomorphic adenoma of oral minor salivary glands: An investigation of its neoplastic potential based on apoptosis, mucosecretory activity and cellular proliferation

ObjectiveThe aim of this study was to investigate the neoplastic potential of the PA of minor oral salivary glands measured by apoptosis (Bcl-2, Bax and p53), mucosecretory activity (MUC1), and cellular proliferation (Ki-67).DesignThirty-one cases of PA of the oral cavity and four controls (C) taken from normal oral minor salivary glands were analyzed using the immunohistochemistry technique. The proteins were detected utilizing a semi-quantitative method (scores) as follows: (−) negative ≤5%, (+) low 6-25%, (++) moderate 26-50% and (+++) high >50% of positive tumour cells. The apoptotic indices were evaluated by the ratio Bcl-2/Bax. Non-parametric comparison and correlation tests were used for analysis.ResultsThe data showed high staining of anti-apoptotic protein Bcl-2 in both groups (PA = 57.9%; C = 67.7%) and a significantly lower expression of pro-apoptotic protein Bax (PA = 22.7%; C = 97.7%) and MUC1 (PA = 14%; C = 82.3%) in PA than in C (p < 0.001). On the other hand, a similar expression of Ki-67 and p53 proteins (≤5%) was seen in both PA and C. In PA, only 2/31 cases showed the ratio Bcl-2/Bax < 1.There was no difference in cellular expression with regard to clinical variables or clinical outcome (p > 0.05).ConclusionThe neoplastic potential of PA could be associated with an imbalance in apoptotic processes and a lower index of cellular proliferation. Mucosecretory activity does not play a significant role in primary PA.