An electron microscopic histochemical study of the histogenesis of major salivary gland pleomorphic adenoma.

Six pleomorphic adenomas were studied histochemically by electron microscopy after staining with ruthenium red, high iron diamine-thiocarbohydrazide-silver proteinate (HID-TCH-SP), and tannic acidferric chloride (TA-FeCI3); the latter two are quite specific for sulfated glycoconjugates. With ruthenium red staining, the proteoglycans of the myxochondroid stroma could be visualized as numerous extracellular 25 to 50-nm polygonal matrix granules with fine projecting filaments. Similar positive ruthenium red-stained intracellular granules were observed within the Golgi-derived vacuoles of the modified “myoepithelial” cells in the myxochondroid region. Secretion of these granules by exocytosis was occasionally observed. The modified myoepithelial cell in the myxoid region exhibited strong HID-TCH-SP- and TA-FeCI3-reactive sites within the Golgi-derived vacuoles. The intercellular space or microcyst of the cellular clusters and the extracellular matrix granules stained strongly positive with both HID-TCH-SP and...