Megakaryocytic myelosis in a cat

A myeloproliferative disorder in a cat was characterized by abnormal proliferation of megakaryocytes in the bone marrow and by severe, nonregenerative anemia. The number of circulating thrombocytes was increased markedly, with many giant and morphologically bizarre forms. Terminally, the circulating blood contained large numbers of undifferentiated blast cells. The spleen and liver were infiltrated by megakaryocytes and mononuclear mesenchymal cells of uncertain identity.