Lung Carcinoma of Sheep (Jaagsiekte). II. Histogenesis of the Tumor

Abstract

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 observed between normal alveolar epithelial cells. On the edges of the tumor nodules the cells formed adenomatous structures, whereas in central regions, there was intense proliferation of cords, and sheets or nests of anaplastic epithelial cells formed carcinomas, often with a sarcomatous stroma. In large tumor nodes, more differentiated sarcomatous elements covered large areas, giving them a fibrous character. The relationship between the neoplastic cells is discussed. Cytochemical examination revealed that most neoplastic cells contained cytoplasmic glycogen granules; some had phospholipid granules. 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 cytochemical methods and electron microscopy.