Five nasal and paranasal papillomas were examined microscopically (i. e, stereoscopically and histopathologically) and ultrastructually (i. e. scanning electron microscopically and transmission electron microscopically).
The following results were obtained.
1. Characteristics of stereoscopical findings
The surface of papilloma showed various findings comparatively smooth surface; shallow dendritic or reticular wrinkles; a mass of coarsely granular or papillary prominence; many sharkskinlike spinous processes.
There was a correlation between the appearance of the hematoxylin-stained surface and the histological findings. That is, the area consisting of columnar epithelia was uniformly stained; that consisting of columnar epithelia and transitional epithelia or squamous epithelia was stained irregularly; that consisting of transitional epithelia was poorly and irregularly stained; that consisting of squamous epithelia and that lacking epithelia were not stained.
2. Characteristics of histopathological findings
The surface of papilloma was characterized by metaplasia. Papillomatous epithelia were composed of one or mixture of ciliated columnar epithelia, transitional epithelia, and stratified squamous epithelia. According to the growth of papillomas, they can be classified into exophytic or inverted. Papillomas observed in this study revealed both exophytic and inverted growth. Mitosis was observed in all cases and some differentiating cells also showed mitosis. Abundant inflammatory cells were observed in the intraepithelial layers and the stroma. Slightly atypical cells were observed.
3. Characteristics of scanning electron microscopic findings
Ciliated cells, secretory cells, and non-ciliated cells were observed in the area consisting of columnar epithelia. Only non-ciliated cells were observed in the area consisting of transitional epithelia. Only squamous epithelial cells were observed in the area consisting of squamous epithelia. Papillomas consisted of one or mixture of these epithelia. In general, the papilloma was characterized by many exfoliative cells.
4. Characteristics of transmission electron microscopic findings
Mitotic figures were frequently observed especially in the basal cells and sometimes observed in the differentiating cells.
Fragmentation and loss of the basement membrane were rarely observed. Some of the basal cells were protruded into the stroma.
The superficial cells consisted mainly of cells which had degenerated, had been exfoliated, and were immature.
Virus-like particles were not observed.
These histological findings (namely metaplasia, fragmentation of the basal membrane, mitoses of the intermediate cells and others) of nasal and paranasal papilloma are sometimes in accordance with those in cases of cancer. Therefore, it was suggested that papillomas are morphologically located between cancer tissues and normal epithelial tissues.
