Histological and ultrastructural morphology of 7,12 dimethylbenz(alpha)-anthracene carcinogenesis in hamster cheek pouch epithelium.

The epithelial changes observed during hamster cheek pouch-DMBA carcinogenesis were classified as hyperplasia, dysplasia and carcinoma stages; carcinomas were usually well differentiated. During carcinogenesis, epithelial thickness increased and in dysplasia and carcinoma stages superficial cells exhibited a marked shift from ortho- to parakeratinization. Marked changes in intercellular organelles were observed and intracellular spaces increased progressively in size. Desmosomes were less commonly seen during carcinogenesis whereas the frequency of gap junctions appeared to increase. The epithelial-connective tissue junction exhibited prominent changes with increasing irregularity, discontinuity and duplication of the lamina densa and a decreasing frequency of hemidesmosomes. Cytoplasmic processes, some containing lysosomal dense bodies, often passed through breaks in the lamina densa and extended into a relatively structureless connective tissue. The results are discussed in relation to the changes in cellular organelles occurring in abnormal epithelial differentiation mediated by the carcinogen and to possible factors which might be involved in the process of cellular invasion.