Adenocarcinoma of the lung in a Steller sea lion (Eumetopias jubatus).

The histological and ultrastructural characteristics of an adenocarcinoma of the lung are described in an about 16-year-old female Steller sea lion with a 1.5 month history of cough and anorexia. The animal had multiple neoplastic nodules in the lungs and diaphragmatic pleura. The bronchial and mediastinal lymph nodes were replaced by neoplastic tissue, and there were several metastatic lesions in the liver and spleen. The lung tumor was characterized by accumulations of encapsulated lesions with central necrosis, and the neoplastic cells showing a papillary growth pattern produced small amounts of mucin. Ultrastructurally, some cells contained basal bodies, and cilia were rarely seen. This neoplasm was considered to be of ciliated bronchial or bronchiolar epithelium origin.