Ultrastructural alterations in experimental lingual leukoplakia and carcinoma.

Epidermoid carcinomas, preceded by dysplastic leukoplakic lesions, were produced on the right lateral borders of the tongues of Syrian hamsters by the application, three times per week, of DMBA in acetone after the area had been scratched with a root canal broach. Animals were killed at 12 to 13 weeks and 15 to 16 weeks. Electron microscopic studies of both the dysplastic leukoplakic lesions and the well-differentiated epidermoid carcinomas revealed clumping of tonofilaments and widening of intercellular spaces, in addition to the cellular pleomorphism, altered nuclear-cytoplasmic ratio, and prominent nucleoli observed with the light microscope. In the carcinomas, there were variations in the morphology of mitochondria, with tubular forms in evidence. The basal lamina in the carcinomas was discontinuous. Pseudopodia arising from basal cells were seen in areas of basal lamina discontinuity.