Spontaneous Hemangiosarcoma of Bone with Hepatic and Pulmonary Metastasis in a Rhesus Macaque (Macaca mulatta): A Case Report

Hemangiosarcoma is a malignant neoplasm of vascular endothelial cell origin that is rare in nonhuman primates (NHPs) and humans. This report describes the clinical, gross, and histopathologic findings of metastatic hemangiosarcoma in a rhesus macaque. A 4.8-year-old female Indian-origin rhesus macaque presented to the Tulane National Biomedical Research Center clinic with right hindlimb lameness and poor body condition. On physical examination, there was significant muscle atrophy of the right leg and pelvis. Radiographs revealed severe bone degeneration and lysis of the right tibia with pulmonary nodules. On necropsy, the right tibia was markedly thickened at least two times the normal size. Multifocal, 1- to 7-mm-diameter dark red nodules were present in the periosteum, compact cortical bone, and medullary cavity. Multifocal dark red nodules measuring 1-10 mm were present in the liver and lung. Histologically, the nodules were composed of neoplastic endothelial cells forming irregular vascular clefts and anastomosing vascular channels. Neoplastic cells often wrapped collagenous stroma. Neoplastic cells stained positive with CD31, as well as with von Willebrand factor immunohistochemical stains. Hemangiosarcoma in NHPs is exceptionally rare. To our knowledge, this represents the first case of metastatic hemangiosarcoma originating in bone in an NHP.