Lung carcinoma of sheep (Jaagsiekte). 11. histogenesis of the tumor 9

In a study of the sheep lung tumor (Jaagsiekte) different areas of the tumor varied in pathological pattern. Near tumor nodules, neoplastic cells, apparently derived from B-type cells, were observedbetween normal alveolar epithelial cells. On the edges of the tumor nodulesthe cells formed adenomatous structures, whereas in central regions, therewas intense proliferation of cords, and sheets or nests of anaplastic epithelialcells formed carcinomas, often with a sarcomatous stroma. In large tumornodes, more differentiated sarcomatous elements covered large areas, giving them a fibrous character. The relationship between the neoplasticcells is discussed. Cytochemical examination revealed that most neoplasticcells contained cytoplasmic glycogen granules; some had phospholipidgranules. Many cells contained both types of granules in different proportions. Alkaline phosphatase activity was also detected in many tumor cells. Cytoplasmic inclusion bodies, which different authors have reported to be developmental stages of a viral agent, were found in this study to be cytoplasmic mucin droplets. This finding was substantiated by various cyto-chemical methods and electron microscopy.—J Nat Cancer Inst 47:197-205, 1971.