Spontaneous renal lymphosarcoma in a juvenile cynomolgus monkey (Macaca fascicularis).

Spontaneous lymphosarcoma, likely of renal origin, was diagnosed in a naive, juvenile, male cynomolgus monkey (Macaca fascicularis). Histologically, renal architecture was effaced by dense infiltrating sheets of plump cells with indistinct borders and scant amphophilic cytoplasm. Mitoses were uncommon. Similar neoplastic infiltrates were also present in the right renal cortex, one adrenal medulla, the prostate, seminal vesicles, myocardium, and the pulmonary interstitium. Serological tests were negative for infection with Simian Immunodeficiency Virus (SIV), Simian T-Lymphotropic Virus-1 (STLV-1), and Simian Retrovirus-5.