The clinical, radiological and pathologic features of a biphasic synovial sarcoma in the left elbow joint of a two-year-old male Rottweiler are presented. The tumor showed positive immunoreactivity for vimentin, Epithelial Membrane Antigen (EMA), p53 and PCNA, while it was negative for the cytokeratin used, S-100, Rb and p21. Immunohistochemistry for EMA allowed the identification of epithelioid components of synovial sarcoma, and may, therefore, contribute in establishing a diagnosis of biphasic synovial sarcoma. Intratumoral variation in PCNA immunoreactivity was minimal, indicating that the various tumor components proliferate at more or less similar rates. Overall, the characterized immunohistochemical profile for canine synovial sarcoma, not defined previously, may provide clues to the histogenesis of the phenotypically mesenchymal and epithelial elements of the tumor, and may be of value in the differential diagnosis of challenging cases, decreasing the risk of under- and mis-diagnosis. Although more cases need to be studied to determine whether there is a consistent pattern of immunostaining in canine synovial sarcoma, its potential significance is discussed in relation to the histogenesis, molecular pathology and differential diagnosis of canine synovial sarcoma.
Animals ; CA-15-3 Antigen/analysis ; Dog Diseases/*pathology/radiography ; Dogs ; Elbow Joint/abnormalities/pathology/radiography ; Forelimb ; Histocytochemistry/veterinary ; Immunohistochemistry/veterinary ; Keratins/analysis ; Male ; Oncogene Protein p21(ras)/analysis ; Proliferating Cell Nuclear Antigen/analysis ; Retinoblastoma Protein/analysis ; Sarcoma, Synovial/chemistry/pathology/radiography/*veterinary ; Soft Tissue Neoplasms/chemistry/radiography/*veterinary ; Tumor Suppressor Protein p53/analysis ; Vimentin/analysis

Multilobular tumour of bone (MTB) is an uncommon tumour and is usually located in the skull. A 13-year-old mixed breed dog was presented with a two-week history of progressively worsening vestibular dysfunction and cognitive abnormalities; it appeared demented and showed asymmetric ataxia and hypermetria of all limbs. The owner opted to have the animal euthanised. Necropsy revealed a large mass occupying the right occipital, parietal and temporal bones, severely compressing the cerebellum and the right occipital lobe. Histologically, it was characterised by the presence of multiple lobules containing osteoid or cartilage and separated by fibrous septae, features typical of MTB. Lung metastases were evident. To our knowledge, this is the first report of an MTB causing both severe cerebral and cerebellar compression and the second detailed report of an MTB of the occipital bone. MTB should be included in the differential diagnosis of bone tumours as well as in cases with central vestibular disease.
Animals ; Dog Diseases/*diagnosis/pathology ; Dogs ; Male ; Skull/*pathology ; Skull Neoplasms/diagnosis/pathology/*veterinary