Salivary gland neoplasms : studies on the cytoskeleton, the secretory apparatus and the nuclear DNA content
Sammanfattning: The heterogeneity of salivary gland neoplasms have made classification and prognostication of these tumours sometimes difficult, and the introduction of techniques, such as enzyme and carbohydrate histochemistry and electron microscopy have only to a certain extent increased our knowledge in these respects. In the present study immunohistochemical methods have been used to identify intermediate filament proteins (IFP) in normal fetal and adult parotid glands, as well as in salivary neoplasms. The intermediate filaments (IF) make up the cytoskeleton in eucaryotic cells. Epithelial tissue contains IF composed of different cytokeratins (CK 1-19) whilst mesenchymal tissue generally contains IF composed of vimentin, and the IFP pattern is very stable even during cell transformation. It would thus be possible to further clarify the histogenesis of salivary neoplasms by identifying IFP, in addition the IFP pattern would probably be useful in tumour typing. Furthermore, ultrastructural cytochemical studies, microspectorphotometry on nuclear DNA as well as enzyme secretory studies of certain tumour types were carried out, in order to further characterize the biology of salivary neoplasms.The immunohistochemical investigations showed that in normal parotid tissue, the different cell types differed in IFP expression: acinar cells express mainly CK 18 and myoepithelial cells mainly CK 17 and 19, whilst duct cells contained a broad range of CK. Vimentin could in addition to CK be detected in myoepithelial cells and basal cells of excretory ducts. Fetal parotid cells showed a similar CK pattern as mature duct cells. In addition, vimentin could be found in some basal cells of the terminal tubules of the fetal glands. Salivary neoplasms could be divided into three types with regard to their IFP pattern: Acinic cell carcinomas showed a CK-pattern similar to normal acinar cells but a co-expression of CK and vimentin was present in some cells. Adenoid cystic carcinomas, mixed tumours and basal cell adenomas showed a CK-pattern of normal duct or myoepithelial cells. The peripheral cells were also vimentin positive. 3. Mucoepidermoid carcinomas and adenocarcinomas had a similar CK-pattern as duct cells, and no tumour cells contained vimentin. This indicates that typing of IFP may be useful for subgrouping of salivary neoplasms.By stereological measurements, the cells of acinic cell carcinomas were found to be very similar to normal parotid acinar cells. Furthermore, they contained amylase and after stimulation by norepiphrine a secretory response was induced, with a rise in intracellular cAMP as well as a release of amylase. By single cell measurements of nuclear DNA content, no difference was found between acinic cell carcinomas with definite metastasis and those without recurrence, both in paraffin sections and cytological smears.
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