Renal osteosarcoma in a dog

A seven-and-a-half-year-old dog presented with anorexia, lethargy and haematurla. A 1.8 kg abdominal mass was excised and determined to be a primary renal osteosarcoma. Haematuria was observed five months after surgery and the tumour was radiographically determined to have recurred locally. The dog was euthanased 12 days later due to refractory pain and anorexia. Although osteosarcomas are expected to develop distant metastases, this dog was euthanased due to clinical evidence of local tumour recurrence. Haematuria was an indication both of initial tumour development and later recurrence.     

Meningeal osteosarcoma in a dog

A meningeal osteosarcoma was diagnosed in a dog displaying neurologic signs compatible with a space-occupying cerebellar lesion. Gross lesions, restricted to the brain, consisted of a solitary, compressive mass attached to the dura mater overlying the left cerebellum. The mass was composed of single and multinucleated, atypical polygonal cells that lined or rested within lacuna surrounded by eosinophilic, mineralized matrix. The matrical component stained dark green-yellow to blue with Movat's pentachrome stain, deep blue to red with Heidenhain aniline blue stain, and brown-black with Von Kossa stain. Results of these stains were interpreted as tumor osteoid. Foci of dural mineralization and osseous metaplasia were present at the point of tumor attachment. The microscopic observations were interpreted as an osteosarcoma of extraskeletal origin. To our knowledge, these findings represent the first documented case of a meningeal osteosarcoma in a domestic animal species.     

Intraocular osteosarcoma in a dog

A 10-year-old German shepherd dog was presented with unilateral uveitis and hyphaema. Treatment was unsuccessful and the eye was enucleated. Intraocular osteosarcoma was diagnosed by histological examination.     

Extraskeletal osteosarcoma of the liver in a dog

An extraskeletal osteosarcoma of the liver is reported in a 14-year-old male Fox Terrier. Ante- and post-mortem radiographs showed calcified nodules in the liver and non-involvement of the skeletal system. The liver was diffusely involved with greyish, mostly mineralized nodules, and metastatic lesions were seen in the diaphragm, omentum, mesentery, and the sternal lymph nodes. Besides the osteosarcoma, a melanoma with metastasis to the regional lymph node was seen in the left hock region.     

Primary osteosarcoma of the synovium in a dog

An eight-year-old, spayed female Labrador retriever was presented for evaluation of left thoracic limb lameness. Radiographs of the left elbow revealed mineralization of the soft tissues surrounding the joint, with no evidence of periarticular bony lysis. Biopsy of the synovial tissues of the left radiohumeral joint yielded a diagnosis of osteosarcoma (OSA). The dog was treated with palliative radiotherapy, piroxicam, and carboplatin chemotherapy, which resulted in excellent pain control for approximately eight months. Amputation of the affected limb was then performed. Six months later, the dog developed multiple subcutaneous OSA metastases, and the dog was euthanized 15 months after diagnosis due to refractory vomiting. This report documents the first known case of primary OSA of the synovium in any species.     

High-grade surface osteosarcoma in a dog

A case of a high-grade surface osteosarcoma in the thoracic limb of a dog is reported. Radiographically, there was no bone involvement but there was increased soft tissue opacity. An aggressive osteosarcoma was diagnosed on the basis of early metastatic disease and histopathological examination. Previously reported surface osteosarcomas in the dog have been periosteal and parosteal osteosarcomas which are generally considered to have a low to intermediate biological activity. The tumour described here had radiographical, gross pathological, histopathological and biological features consistent with human high-grade surface osteosarcoma. The characteristics of surface osteosarcomas are briefly reviewed.     

Vertebral telangiectatic osteosarcoma in a dog

Telangiectatic osteosarcoma (TOS) affecting the seventh cervical vertebra (C7) was diagnosed in a 4-year-old male dog with signs of locomotor dysfunction. Bone lysis and an extradural-extramedullary mass were observed in radiographs and occipital myelograms. The diagnosis was confirmed by histopathologic and immunohistochemical examination of the mass. The tumor was composed of large blood-filled cavities lined by anaplastic stromal cells (malignant osteoblasts). Around the cavities were characteristic tumor giant cells ("bizarre cells"). Immunohistochemically the tumor cells were positive for proliferating cell nuclear antigen. The lining cells of the cysts were negative for von Willebrand factor. The histologic findings in this case of TOS involving C7 were similar to those seen in other cases of TOS in dogs and in people. Immunohistochemistry was a useful tool for assessing malignancy and for ruling out other differential diagnoses.     

Primary ocular osteosarcoma in a dog

An adult male Rottweiler presented to the veterinary medical teaching hospital at Purdue University with a 1-month history of hyphema. On physical examination conjunctivitis, episcleral hyperemia, corneal edema, hyphema, mild glaucoma and loss of vision were observed in the left eye. No other abnormalities were found. The left globe was surgically removed because of the high likelihood of neoplasia and it was fixed in 10% buffered formalin and submitted for pathology. A histologic diagnosis of primary osteosarcoma of the eye was made. Radiographic evaluation did not reveal any evidence of other tumors or pulmonary metastasis. This is the fourth canine case of primary intraocular osteosarcoma to be documented.     

Primary pulmonary osteosarcoma in a dog

An 11-year-old mixed breed dog was referred because of coughing and painful swelling of the distal extremities which had not resolved with antibiotic treatment. A consolidated left cranial lung lobe and hypertrophic osteopathy were identified by radiographs. A unique feature of this report is the marked, rapid reduction in pain and lameness associated with hypertrophic osteopathy after treatment with corticosteroids. Histological examination of an 8 cm diameter, spherical mass found in the excised cranial lung lobe revealed osteosarcoma. No evidence of local or distant metastases was present. The dog survived one year after diagnosis.     

Multilobular tumor of the mandible in a Pekingese dog

Multilobular tumor of bone detected in a 2.5-year-old male Pekingese dog is reported. Grossly, the neoplasm consisted of multiple, variably sized, gritty, grayish-white to yellow nodules separated by thick collagenous septa. Histologically, these nodules contained multiple lobules of irregularly shaped and sized islands of well-differentiated osteoid and cartilage, separated by anastomosing fibrovascular septa. Chondrocytes and osteocytes were observed in the lacunae and in more osseous islands in the lobule, respectively. These lobules were surrounded by mesenchymal spindle cells. Mitotic figures were not evident. The neoplastic pattern was consistent with that of a multilobular bone tumor. Diagnosis was based on gross and light microscopic findings. The cause of this neoplasm was not determined.     

Primary mesenteric root osteosarcoma in a dog

Abstract: A 10‐year‐old spayed female Boxer‐mix was presented with a history of several weeks of soft stools, straining to defecate, inappetance, and lethargy and several days of hematochezia, melena, and dyschezia. Physical examination findings included mild tachycardia and tense cranial abdomen. CBC results indicated moderate mature neutrophilia. Ultrasonographic examination of the abdomen revealed a large mass with complex echogenicity in the cranial abdomen, likely associated with the intestines. Cytologic examination of a fine‐needle aspirate revealed a population of round, stellate, and spindle‐shaped cells arranged individually and in aggregates with occasional cells embedded in an eosinophilic extracellular matrix. The cytologic interpretation was malignant mesenchymal neoplasm with osteosarcoma being the primary differential. Surgical exploration of the abdomen revealed a 10‐cm‐diameter mass located at the intestinal mesenteric root. The mass occluded blood flow to portions of the gastrointestinal tract. The dog was euthanized due to the nonresectable nature of the tumor. Histopathologic examination revealed an expansile poorly demarcated mesenchymal neoplasm composed predominantly of spindloid and pyriform cells, occasionally embedded in a matrix compatible with osteoid. The diagnosis was extraskeletal osteosarcoma of the intestinal mesenteric root, only rarely reported in dogs.     

Multilobular tumor of bone in the mandible of a dog

An 8-year-old Siberian husky dog was presented for a mass involving the rostral mandible. Intraoral radiographs demonstrated diffusely irregular bone and displacement of all mandibular incisor teeth. The mass was diagnosed as a grade I multilobular tumor of bone based on incisional biopsy. A bilateral rostral mandibulectomy was performed with tumor negative margins. Oral examination at 14-months following surgery indicated normal healing with minimal side effects and no evidence of tumor recurrence.     

Extensive bilateral odontogenic cysts in the mandible of a dog

A 5-year-old female neutered Boxer dog was diagnosed with extensive odontogenic cysts that affected the left and right mandibles. Rostral mandibular swelling was detectable clinically, and bilateral cystic mandibular lesions were identified radiographically. The dog's owners elected for euthanasia. A full postmortem was performed. Cystic cavities were confirmed in the body of each mandible, extending from the incisor teeth to the mid premolar region. Incisor, canine, and premolar tooth roots indented each cavity. Histologic examination of the cystic cavities reflected an inner lining of attenuated stratified squamous epithelium overlying a fibrous layer infiltrated by a mixed, predominantly mononuclear, inflammatory infiltrate.