Histopathological studies of the labial salivary glands in patients with Sjögren's syndrome. Part II: electron microscopic study.

The ultrastructural changes in the labial salivary glands, in which was demonstrated light microscopically the characteristic appearance of Sjögren's syndrome, were investigated in 12 cases. The significance of the following findings in this syndrome was discussed. The infiltrating cells were chiefly composed of small and medium sized lymphocytes and plasma cells. There were also found large lymphocytes with mitosis and morphologically regarded as T-lymphocytes. A small number of histiocytes and other mononuclear cells scattered among them. The remaining secretory cells were degenerated with disturbance of the secretory process. Degeneration, destruction, squamous metaplasia and proliferation of the duct epithelial cells were associated with mononuclear cell infiltration, and these changes were more conspicuous in the intercalated regions. The basal laminae of the acini and ducts were in part markedly thickened with high electron density. The epimyoepithelial islands in varying forms and sizes were composed of morphologically different kinds of cells which were probably derived from the duct cells. Only a few myoepithelial cells were located in the peripheral portion of the epimyoepithelial islands and there was no proliferation of myoepithelial cells. The hyaline-like substance, occasionally appearing in and around the epimyoepithelial islands, was an accumulation of fine fibrillar substance. Virus-like or tubuloreticular structures were found in the endothelial cells in 1 case.