B-cell lymphoma invading and compressing the heart base and pericardium in a cat.

A 3-year-old, 3.5-kg, neutered male, domestic shorthair cat presented with progressive lethargy, anorexia, coughing, and acute respiratory distress of two-week duration. Auscultation detected diffuse pulmonary crackles. Lung sounds were absent over the left cranial thorax. Sinus tachycardia was recorded. Thoracic radiographs revealed cardiac silhouette enlargement, dorsal displacement of the carina, and uniform, soft tissue opacity in the left cranial hemithorax. Transthoracic two-dimensional echocardiography revealed a large mass within and external to the pericardial space, effacing the pericardium, and compressing basal cardiac structures. The point-of-care feline immunodeficiency virus and feline leukemia virus test was negative. Euthanasia was elected, and permission for necropsy granted. Gross postmortem evaluation revealed a prominent mediastinal mass that effaced the left cranial lung lobe and invaded the heart base and pericardium. The mass was confirmed as B-cell lymphoma by histopathology and immunohistochemistry.