A 5-year-old Holstein cow presented with the clinical signs of heart failure. A complete blood cell count showed moderate lymphocytosis. The necropsy indicated replacement of normal myocardium by firm scirrhous tissue. Some affected areas in the endocardial surface showed irregular nodular appearance. Histological exami-nation revealed dense sheets of lymphocytic and lympho-blastic neoplastic cells resulting in the complete obliteration of the normal architecture of the heart. The final diagnosis was intermediate-grade lymphosarcoma.
