ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY OF SALIVARY DUCT CARCINOMA OF THE PAROTID-GLAND

A case of salivary duct carcinoma of the parotid gland found in an 81- year-old man was studied by light microscopy, immunohistochemistry, an d electron microscopy. Histologically, the tumor was composed of elong ated cords of cells and ductal structure with desmoplastic stromal rea ction. Tumor cell nests sometimes showed central comedonecrosis. Immun ohistochemically, the tumor cells were positive for cytokeratin and ep ithelial membrane antigen, and they were negative for S-100 protein an d muscle-specific actin. Electromicroscopically, two cell types were i dentified. The first cell type showed electron-lucent cytoplasm with s cant organelles. The second type cell contained numerous mitochondria. Neither acinar nor myoepithelial cell differentiation was observed. T hese findings suggest that salivary duct carcinoma originates from the interlobular or excretory ducts.