An ultrastructural morphometric study of cellular and nuclear volume alterations during experimental oral carcinogenesis.

Cellular and nuclear pleomorphism are features of epithelial dysplasia, a premalignant alteration found in many stratified squamous epithelia including those of the oral mucosa. In the present report we have applied morphometric techniques to evaluate alterations in cellular and nuclear volume during epithelial differentiation in experimentally-induced oral carcinogenesis. Hamster cheek pouches treated with DMBA were biopsied and assigned to hyperplasia, dysplasia and carcinoma groups with untreated pouches being used as controls. Following a rigorous sampling scheme, electron micrographs from defined basal, spinous and granular strata were obtained and cellular and nuclear volumetric estimates obtained by a combination of direct measurement and stereological intersection counting. In all strata, nuclear, cytoplasmic and cellular volumes were lowest in the normal control group and were increased in all experimental groups. Volumetric estimates obtained for carcinogen-treated groups were generally between 2 to 3 times higher than for the control group which indicates that cellular and nuclear hypertrophy occurs in conjunction with the epithelial hyperplasia and proliferation induced by the chemical carcinogen. We also describe the application of the pathological alteration ratio (PAR), a parameter which is independent of methodological variables, and which was consistently elevated in our experimental study. This was also applied to a number of reports in the literature which describe morphometric alterations in cellular or nuclear parameters in a variety of human lesions. Within any particular group of lesions, PAR values were generally higher for carcinomas than for other benign conditions. We conclude that cellular and nuclear hypertrophy occurs not only during experimental carcinogenesis but also in human benign and malignant lesions. With the advent of computer-based automated image analysers, measurements of certain structural features on sectioned tissues may have a role in histopathological diagnosis.