Immunohistochemical localization of placental glutathione S-transferase (GST-pi) in normal and inflammatory salivary glands (74 cases) and tumors (71 cases) was studied. In the normal and inflamed salivary glands of all locations (including major and minor salivary glands), the ductal epithelial cells showed moderate to strong GST-pi staining, myoepithelial cells showed weak staining and the acinar cells were negative. The staining pattern of the tumor cells was similar to that of their normal counterparts. The tumor cells were generally positive with GST-pi staining except those tumor cells demonstrating acini differentiation (serous cells in acinic cell carcinoma, mucous cells in mucinous cystadenoma and mucoepidermoid carcinomas). Most of the salivary gland tumors, benign or malignant, showed a weak GST-pi staining. Only mucoepidermoid carcinomas demonstrated significantly increased GST-pi reactivity compared to other tumors (p<0.0001), which may be a reflection of both malignancy and squamous differentiation of the tumor. The marked increase in GST-pi activity in mucoepidermoid carcinomas may be useful in serological screening of recurrent and metastatic mucoepidermoid carcinomas.

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