J Med Primatol. 2017;46:51–55. wileyonlinelibrary.com/journal/jmp | 51 © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Accepted: 9 January 2017 DOI: 10.1111/jmp.12254 CASE REPORT Spontaneous telangiectatc osteosarcoma in a rhesus macaque (Macaca mulata) B. Goldschmidt 1 | M.I.Z. Calado 1 | F.C. Resende 1 | R.M. Caldas 2 | L.W. Pinto 3 | C.A.A. Lopes 1 | F.G.O. França 4 | B.S. Meireles 1 | I.V. Souza 1 1 Serviço de criação de primatas não humanos, Insttuto de Ciência e Tecnologia em Biomodelos (ICTB), Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro, Brazil 2 Laboratório de Pesquisa Clínica em Dermatozoonoses em Animais Doméstcos, Insttuto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil 3 Divisão de Patologia, Insttuto Nacional de Câncer, Rio de Janeiro, RJ, Brazil 4 Setor de radiologia, Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil Correspondence Beatriz Goldschmidt, Serviço de criação de primatas não humanos, Insttuto de Ciência e Tecnologia em Biomodelos (ICTB), Fundação Oswaldo Cruz (FIOCRUZ), Avenida Brasil, Rio de Janeiro, Brazil. Email: bibi@focruz.br Abstract Osteosarcoma (OS) is the most common type of bone cancer, especially in young. Telangiectatc osteosarcoma (TO) is a rare variant of OS, and hence, its occurrence, presentaton, and prognosis are poorly understood. A 4-year-old female rhesus mon- key presentng lameness and swelling was examined for a mass on the right humerus. Radiography revealed fracture and disorganized structure of bone tssue. Histopathological examinaton revealed malignant neoplasm composed of anaplastc osteoblasts, which invaded the bone marrow and surrounded blood-flled cysts in the epiphysis and diaphysis forming septa. Cytogenetc analysis showed aneuploid cells, supernumerary AgNORs, and a marker fragment. The neoplasm was diagnosed as TO. To our knowledge, the occurrence of TO and its cytogenetc analysis were reported for the frst tme in non-human primates. KEYWORDS bone cancer, chromosomes, non-human primate, osteosarcoma 1 | INTRODUCTION Osteosarcoma (OS) is the most common primary malignant bone tumor in humans, dogs, and cats. 1 In non-human primates, sponta- neous OS is rarely described and only few cases can be found in the literature in rhesus macaques (Macaca mulata). 2-4 Telangiectatc osteosarcoma (TO) is one of the rare subtypes of OS. It accounts for about 3%-10% of all human OSs with a preponder- ance of males and occurs mainly in the younger age group. The most common locaton at presentaton is the metaphyses of long bones. The distal femur is involved most frequently, followed in frequency by the proximal tbia and proximal humerus. 5 This type of OS has not been described in non-human primates. Although conventonal OSs may contain telangiectatc elements, only those composed almost entrely of telangiectatc tssue are generally considered true exam- ples of this entty. The most common and most important diferental diagnostc consideraton is aneurismal bone cyst (ABC). The radio- graphic and gross appearances of TO and ABC show varying simi- larites. 5 Another important diagnostc consideraton includes giant cell tumor of bone. The histologic appearances of these enttes are very diferent and are easily distnguishable from TO. The presence of vascular spaces lined only by endothelial cells and the absence of osteoid in the hemangiosarcoma are the key histologic features used to diferentate hemangiosarcoma from TO that needs to be consid- ered in the diferental diagnosis for a lytc bone tumor that appears to be malignant. Telangiectatc osteosarcoma is an aggressive tumor that destroys pre-existng bone and forms blood-flled cysts lined by malignant osteoblasts that form septae, with or without producton of osteoid. 1,5 Radiographically, TO appears as purely lytc destructve lesions mainly located in the metaphyses and afectng the medullary and cortcal bones, with poorly demarcated margins. 5 The exact cause of TO is unknown; however in humans, the familial occurrence in cousins suggests a genetc partcipaton. 6 The defniton of alteratons has increased from visualizaton at the chromosome level to point with OS mutatons, but the genetc etology of OS is stll unknown. 7 Conventonal cytogenetc studies have demonstrated that OS exhib- its high karyotype heterogeneity, with diferent degrees of aneuploidy and complex structural rearrangements. Although many cytogenetc