Pulmonary carcinoma (Jaagsiekte) of sheep. Ultrastructural study of early and advanced tumor lesions.

Lung carcinoma of sheep (Jaagsiekte) is a bronchiolar-alveolar cell carcinoma. Differences in the ultrastructural patterns of early and advanced lesions of the disease are described. A-type and C-type viruses were observed in advanced tumors and were absent in early lesions. Numerous microtubules were characteristic in the epithelial tumor cells of the early lesions and were absent in the advanced tumor. In comparison to the early lesions, extensive cytosome production, surfactant secretion, and glycogen accumulation were observed in the advanced tumor. The immune response to the early tumor lesion was restricted to the peribronchiolar lymph aggregates, while in the advanced stages of the disease the systemic immune response was markedly increased.