Ultrastructure of normal epithelial cells in Papanicolaou-stained cervical smears. An application of a modified open-face embedding technique for transmission electron microscopy.

The results of an open-face embedding technique applied to Papanicolaou-stained uterine cervical smears are presented. By this technique, cells are smeared on a plastic sheet, fixed in 1.5% buffered glutaraldehyde and stained by the Papanicolaou method; areas of special interest are then selected by light microscopy for electron microscopic observations. Thus, a comparison is possible between the light microscopic characteristics of cells in smear preparations and their ultrastructural counterparts. The good ultrastructural preservation allowed detailed study of nuclei and cytoplasm. The endocervical cells had intact nuclei with nuclear envelope, Golgi apparatus, well-preserved mitochondria and two types of secretory material. The superficial and intermediate squamous cells showed loss of desmosomes; dense, fine cytoplasmic fibrils; small, fatty droplets; and degenerated nuclei with loss of the nuclear envelope. Compared with ultrastructural studies on cervical tissues, the intermediate cells in cervical smears were more degenerated, presumably because predominantly degenerated intermediate cells exfoliate. This study indicates that the light microscopic impression of the nuclear appearance is misleading: in the routine smear the nuclei of superficial and intermediate cells may look "intact" and "well preserved" whereas ultrastructurally the nuclei are degenerated.