Axial Multicentric Osteosarcoma in an English Cocker Spaniel

An 8-year-old, male neutered English Cocker Spaniel presented to the Royal Veterinary College for evaluation of reluctance to exercise and spinal hyperesthesia of 1-year duration. Medical treatment by referring veterinarian with antibiotics and tramadol did not result in clinical improvement. Survey radiographs performed before referral revealed multiple lytic bone lesions involving sternum and ribs. The dog had been fed for several months on a hypoallergenic diet and administered prednisolone for presumed inflammatory bowel disease. General physical examination did not reveal abnormalities. Neurological examination revealed a kyphotic posture and a short and stilted pelvic limb gait. Spinal hyperesthesia could be elicited on thoracic, thoracolumbar, and lumbar spinal palpation. A complete blood count and free catch urine analysis did not reveal abnormalities. Serum biochemistry profile revealed hypoalbuminemia (20.3 g/L [RI (reference interval) 28– 39 g/L]) and increased inorganic phosphorus concentration (2.68 mmol/L [RI 0.8–2 mmol/L]), alanine aminotransferase activity (234 U/L [RI 13–88 U/L]) and alkaline phosphatase activity (1425 U/L [RI 19–285 U/ L]). Ionized calcium concentration was within the RI. Magnetic resonance imaging (MRI) imaging was performed using a protocol that included sagittal and transverse plane T2-weighted (repetition time, TR [ms], echo time, TE [ms], 3000/120) (Fig 1A), sagittal T2weighted short-tau inversion recovery (TR/TE, 3612/80) (Fig 1C) and sagittal and transverse plane T1-weighted spectral presaturation with inversion recovery (TR/TE, 533/8) sequences. Sagittal and transverse plane T1weighted (T1W turbo spin echo) (TR/TE, 400/8) images were acquired before and after IV injection with gadolinium contrast (Fig 1B, D). Magnetic resonance imaging demonstrated multiple poorly defined, expansile lytic lesions affecting the spinous processes of the sacrum, L5, L3, T13, T12, T11, T8, and T2, the vertebral bodies of the sacrum, L5, L4, T13, T12, T11, T9, T7, T6, and T2, and multiple sternebrae. These lesions were characterized by a heterogeneous intensity in all sequences and patchy contrast enhancement. A fracture of the vertebral body of T11 with bone remodeling was present without spinal cord compression. After MRI, thorax and abdomen computed tomography (CT) was performed using a 16-slice scanner. CT imaging (Fig 2A) confirmed the expansile lytic bone lesions and revealed additional lesions affecting multiple ribs and pelvis and accounting for more than 20 bone lytic lesions with variable sizes. CT did not reveal any abnormalities involving thoracic or abdominal visceral structures and no enhancement was seen after IV administration of contrast medium. Based on imaging and laboratory results, nonproductive multiple myeloma was considered the most likely differential diagnosis. The lack of a clear primary lesion, the numerous bones involved and absence of visceral lesions was not typical for axial osteosarcoma (OS), even considering concurrent multiple metastases. The imaging findings were more suggestive of synchronous multicentric osteosarcoma (MOS), a rare OS clinical presentation in people, with simultaneous multiple bone lesions without pulmonary involvement and extremely rare in domestic animals, which was considered as a rare differential diagnosis. Bone marrow aspirate (left humerus) and serum electrophoresis did not reveal abnormalities and evaluation of urine for Bence-Jones proteins was negative. Ultrasound guided fine needle aspirates of affected lesions (dorsal spinous process of L5 and rib) were inconclusive. Subsequently, the dog was anesthetized and a From the Department of Clinical Science and Services, (Parzefall, De Decker, Carvalho, Lara-Garcia); Department of Pathology and Pathogen Biology, Royal Veterinary College, University of London, Hatfield, (Terr, Smith); and the Veterinary Diagnostic Services, School of Veterinary Medicine, University of Glasgow, Glasgow, UK(Leach). The work was done at the Royal Veterinary College, United Kingdom. No financial support was given for this study. This case was presented in part at the 27th Annual Symposium of the European Society of Veterinary Neurology – European College of Veterinary Neurology, 18–20 September 2014, Madrid, Spain. Corresponding author: A. Lara-Garcia, DVM, MSc, PhD, DACVIM & DECVIM-CA (Oncology), Department of Clinical Science and Services, Royal Veterinary College, University of London, Hatfield, AL9 7TA, UK; e-mail: algarcia57@rvc.ac. uk. Submitted April 29, 2016; Revised July 1, 2016; Accepted July 5, 2016. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. DOI: 10.1111/jvim.14555 Abbreviations: