Primary Splenic Leiomyosarcoma With Metastasis in a Rhesus Monkey ( <i>Macaca mulatta</i> )

Primary mesenchymal tumours of the spleen in non-human primates are exceedingly rare. We report on a 13-year-old female rhesus monkey who had an enlarged liver, spleen and multiple lung masses. Macroscopic, microscopic and immunohistochemical examinations revealed a splenic leiomyosarcoma with widespread metastasis. This is the first report of a splenic leiomyosarcoma in a non-human primate.