Exfoliative cytology of the early lesions of experimental oral cancer in the hamster

Abstract

Malignant epithelial tumours were produced in the cheek pouches of golden hamsters by regular applications of a chemical carcinogen. Exfoliated cell smears were examined from the various periods during transition from the state immediately preceding tumour formation to the development of early malignant tumours. The changes in these smears were compared with the histological and clinical appearances of the same, or similar, tumours. During progression from the benign state to malignancy the most striking features of exfoliated cells were changes in the staining properties of their cytoplasm, in their nucleo-cytoplasmic ratio and in the degree of keratinisation in individual cells. At the onset of malignancy two types of malignant cells appeared; one of these had large, clear nuclei with prominent clumping of chromatin, an increased nucleo-cytoplasmic ratio and vacuolation of the cytoplasm; cells of the other type were smaller, and exhibited dense hyperchromatic nuclei. By comparing smears with sections of the same tumour, a correlation was revealed between the presence of exfoliated cells showing large clear nuclei and the existence of either marked dyskeratosis or well-differentiated carcinoma; smears in which cells with small dark nuclei appeared were found to correspond with sections exhibiting undifferentiated carcinoma and active invasion. Cytological and histological appearances corresponded to one another at all stages of the experiment.