Comparative aspects of cell fine structure in three cases of inverted, Schneiderian papilloma

Three cases of nasal, epidermal, inverted papilloma, one of which involved synchronous carcinoma, were examined at the light and electron microscope level. Case I showed typically stratified squamous epithelial cell fine structure, including interdigitating cell borders with typical desmosome contacts and bundles of intracellular filaments. Epithelial cells of Case II did not have an identical squamous type appearance, they were smoother in outline, lacked extensive cell interdigitation and desmosomes, and were directly apposed to one another. Cells observed in Case III, involving synchronous carcinoma, also failed to reveal extensive stratified squamous epithelial characteristics, but were smooth in outline, lacked extensive interdigitations and desmosomes. On the bases of electron-density, cells in all three biopsies were characterizable as light, intermediate and dark cells. This variation reflects variations in the amount of granular endoplasmic reticulum and non-membrane bound polysomes. Cytological characteristics, including filament formation, filament concentration into bundles, and changes in nuclear structure leading to pyknosis are described. The above data are discussed in terms of their significance and relevance to previous electron microscope studies on various nasal inverted papillomas. It is concluded that fine structure characteristics, as well as light microscopic observations, should be more frequently utilized in identifying malignant as opposed to benign tumors.