[The so-called lung adenomatosis of sheep--an interesting pneumopathy from the comparative pathologic view]

Contrary to conditions in human pathology, primary pulmonary neoplasms are rare in animals. The so-called pulmonary adenomatosis of sheep (PAS) is of greater importance among the epithelial lung tumors of domestic animals. PAS is a chronic, lethal pneumopathy caused by an oncogenic retrovirus. It is associated with the category of slow virus infections for its extremely long incubation period. PAS is characterized as a primary multicentric epithelial neoplasm which develops from proliferating alveolar pneumocytes II and non-ciliated bronchial epithelial cells. It has been recently classified as broncho-alveolar carcinoma on account of its morphological features and occasional metastasis into bronchial and mediastinal lymph nodes. PAS because of its similarity with human pulmonary carcinoma may be used as a model pneumopathy in comparative oncology.