Acute Megakaryocytic Leukaemia (AMKL)-like Disease in a Cynomolgus Monkey ( Macaca fascicularis)

A 5-year-old male cynomolgus monkey ( Macaca fascicularis) with a clinical history of bleeding tendency, severe anaemia, thrombocytopenia and elevated serum concentration of liver-related enzymes was examined post mortem. Ecchymotic haemorrhages were present on the left eyelid and forehead. The liver, kidney and spleen were markedly enlarged and the kidneys had capsular petechiae. Microscopically, numerous atypical cells resembling myeloid cells were observed in the bone marrow, and myelofibrosis was present. Atypical cells were also present in the blood vessels of the liver, kidney, spleen, lymph nodes, lung, heart, bladder, adrenal gland and brain. Some neoplastic cells had oval or pleomorphic macronuclei and others were multinucleated. Immunohistochemically, the majority of the neoplastic cells had granular cytoplasmic expression of the megakaryocyte-associated antigens Von Willebrand Factor and CD61-IIIa, but were negative for myeloperoxidase. A diagnosis of acute megakaryocytic leukaemia (AMKL)-like disease was made. This would appear to be the first report of AMKL-like disease in non-human primates. This monkey was infected with simian retrovirus type D and it is possible that this viral infection was associated with the development of neoplasia.