Spontaneous T/NK-cell lymphoma associated with simian lymphocryptovirus in a Japanese macaque (Macaca fuscata)

A 5-year-old female Japanese macaque (Macaca fuscata) was humanely destroyed because of severe anaemia with poor response to treatment. At necropsy examination, marked splenomegaly and systemic enlargement of lymph nodes were observed. Microscopical examination revealed diffuse proliferation of neoplastic lymphoid cells in the spleen and lymph nodes with infiltration of the liver, lung, gastrointestinal tract, kidney and bone marrow. Immunohistochemically, the neoplastic cells expressed CD3 and CD4, but not CD20, CD79α or CD8, consistent with a T helper phenotype. A portion of neoplastic cells expressed the natural killer (NK) cell marker CD56. In-situ hybridization detected Epstein-Barr virus (EBV)-encoded small RNAs in the neoplastic cells, indicating the involvement of simian lymphocryptovirus (LCV). This is the first report of simian LCV-associated T/NK-cell lymphoma with the predominant expression of T-cell antigens in non-human primates.