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Conclusion: P-glycoprotein is abundantly expressed in certain parotid mucoepidermoid carcinoma tissues, known historically to be multidrug resistant. This discovery may be important in incrementally advancing our ability to develop alternative pharmacologic strategies to improve multi-modality tumor control. Objective: P-glycoprotein plays a functional role in promoting the efflux of drug metabolites in certain malignant tumors. With this understanding we immunohistochemically investigated the expression of P-glycoprotein in parotid mucoepidermoid carcinoma tissues and examined prognostic factors that contribute to the treatment of parotid cancer. Methods: Thirteen patients with mucoepidermoid carcinoma of the parotid gland were included. P-glycoprotein expression was immunohistochemically investigated by a modified avidin-biotin-peroxidase complex method using four different antibodies. Results: P-glycoprotein expression was observed in a higher percentage of patients with higher grade malignancy. The tumor size-related difference in P-glycoprotein expression was only significant for staining with one antibody, and no significant differences were observed with or without induction chemotherapy. [ABSTRACT FROM AUTHOR]