The nuclei of epithelial cells of the uterine cervix of normal women and of patients with various degrees of dysplasia,
carcinoma in situ, and invasive
carcinoma were studied by means of electron microscopy. Nuclear
ribonucleoprotein components and
chromatin were contrasted using preferential methods for
RNA and
DNA. Changes in the distribution of the extranucleolar
ribonucleoprotein-containing structures were found, ranging from low-grade dysplastic lesions to invasive
carcinoma. Compared with normal epithelial cells, dysplastic and neoplastic cells possess more nuclear bodies, as well as deep invaginations of the nuclear envelope and lobulations. Morphometric parameters estimated were nuclear volume, numerical density of perichromatin granules (PCG), and fraction of nuclear volume occupied by compact
chromatin. The pattern of values of these parameters in the cell layers of normal cervical epithelium was disrupted in all the lesions. These data suggest that the processes studied induce early alterations in transcription and processing and/or exportation of
mRNA to the cytoplasm. Two populations of cells were found in invasive
carcinomas, one with large nuclei, sparse compact
chromatin, and few PCG, and the other with small nuclei, abundant compact
chromatin, and numerous PCG. Their morphologic features indicate that the former population is composed of relatively undifferentiated cells, while the letter is made up of well-differentiated cells which could be neoplastic or entrapped normal cells.