Altheugh apoptosis is generally thought to be inhibited in malignant tumors, the phenomenon is not wetl understood in benign tumors. We used the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) method to study apoptosis in pleomorphic adenoma. We found an apoptosis-positive reaction in the nuclei of a few tumor cells that had tubuloductal structures, neoplastic cells in sheets, and myoepithelial cells made up of myxoid structures. More apoptosis-positive

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... cells were found in luminal tumor cells of tubular and duct-like structures. In oral papillomas, some epithelial cell$ showed apoptosis-positive reactions in the nucleus, although very tew positive cells were seen in the five cases of oral squamous cell carcinomas we examined. We concluded that apoptosis tends to occur in ductal epithelial cells in pteomorphic adenoma and that expression of apoptosis in the cells of benign tumors is different from that in malignant tumors such as cancer.