Malignant histiocytosis in a cat.

A 13-year-old male domestic shorthair cat was found to have normocytic hypochromic regenerative anemia, lymphopenia, eosinopenia, thrombocytopenia, hyperglycemia, hyperbilirubinemia, and a prolonged activated partial thromboplastin time. Transfusions of packed RBC failed to maintain the PCV above 13% for > 8 hours. The cat was euthanatized. At necropsy, the spleen liver, lymph nodes, and bone marrow were infiltrated with malignant histiocytes undergoing erythrophagocytosis.