Glycosaminoglycan expression in pleomorphic adenomas of the salivary gland

ABSTRACT

Pleomorphic adenoma is the most common benign tumor in salivary glands, and occurred in frequency of 60% in parotid gland tumors, and 50% in submandibular gland tumors, and 25% in sublingual gland tumors. Histopathologically, pleomorphic adenoma is composed of epithelial cells and mesenchymal tissues, and called 'mixed tumor' because of morphological divergency. The cell structures of luminal area are composed of polyhedral and cuboidal secretory epithelial cells and modified myoepithelial cells around it, and mesenchymal tissue is composed of some myoepithelial cells and stromal tissue. In stromal tissue, myxoid change, chondroid change, or hyalinization can be seen even if bone tissue. In many studies, tumor cells of pleomorphic adenoma containing modified myoepithelial cell participate in synthesis of glycosaminoglycans. In this study, tissue sample of pleomorphic adenoma of human salivary gland were obtained from 20 surgical specimens, and all specimens were routinely fixed in 10% formalin and embedded. Serial 4-8 micrometer thick sections were cut from paraffin blocks. The histopathologic evaluation was done with light microscopy. And, with immunohistochemical staining, characteristics of glycosaminoglycan were observed. And, for biochemical analysis of glycosaminoglycan, isolation of crude glycosaminoglycan from tumor tissue and immuno-blot analysis were carried out. With transmission electromicroscopy, tumor cells and biologic behavior of pleomorphic adenoma were observed with distribution and expression of glycosaminoglycan in tumor cells. The results were obtained as follows 1. In immunohistochemical study, chondroitin 4-sulfate is highly postively stained in myxoid stromal tissue, and chondroitin 6-sulfate is highly positively stained in chondroid mesenchymal tissue, both glycosaminoglycans are positively stained in non-luminal cell of ductal area. 2. Dermatan sulfate and keratan sulfate is positively stained in periductal non-luminal tumor cells. 3. In immunohistochemical study, heparan sulfate is weakly stained in luminal cells and non-luminal cells around duct, and chondroid mesenchymal tissue. 4. In transmission electromicroscopic view, the tumor cells are composed of modified myoepithelial cells, and contain many microfilaments and well developed rough endoplasmic reticulum. 5. In Immuno-Blot analysis, the expression of glycosaminoglycans is expressed mostly in chondroitin 6-sulfate and chondroitin 4-sulfate. From the results obtained in this study, tumor cells of pleomorphic adenoma are composed of modified myoepithelial cells, and glycosaminoglycans of chondroitin 4-sulfate and chondroitin 6-sulfate mostly participate in the development of pleomorphic adenoma, but dermatan sulfate, keratan sulfate and heparan sulfate glycosaminoglycans were expressed variably.