Primary jejunal osteosarcoma associated with a surgical sponge in a dog

Primary jejunal osteosarcoma was diagnosed in association with a surgical sponge in a dog. The tumor was biologically aggressive, resulting in widespread metastasis throughout the abdomen within 2 months of surgical resection. Microscopic examination of the resected osteosarcoma revealed strands of gauze material throughout the tumor mass. It was theorized that the presence of a sponge foreign body may have resulted in malignant transformation of adjacent tissues similar to what has been reported to occur after internal fixation of some long-bone fractures.     

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.     

Extraskeletal osteosarcoma in a cat.

A 7-year-old spayed female domestic shorthair cat was referred for evaluation of a localized growing mass on the left flank. Cytologic and histologic findings suggested that the mass was an extraskeletal osteosarcoma. Radiography failed to reveal any association between the lesion and the axial or appendicular skeleton. Because of the large size of the tumor, the cat was treated with carboplatin prior to and after surgery (hemipelvectomy) to ensure that surgical margins were free of neoplastic cells and to prevent systemic dissemination of malignant cells. The tumor has not recurred during a 2-year follow-up period.     

Hemothorax associated with telangiectatic osteosarcoma in a dog

Hemothorax in a dog was attributed to bleeding from an intrathoracic mass attached to the sixth through the tenth ribs. The mass contained numerous cavernous, blood-filled spaces as well as bands of osteoid and occasional foci of osseous tissue. The diagnosis was telangiectatic osteosarcoma. Telangiectatic osteosarcoma is an uncommon variant of osteosarcoma. Cavernous, blood-filled spaces and paucity of bone are important histologic features. Metastasis was described in one of the seven telangiectatic osteosarcomas reported in dogs, and none was found in this case.     

Fibrosarcoma arising at the site of a retained surgical sponge in a cat

Abstract: An 8‐year‐old female spayed domestic shorthair cat had an abdominal mass palpated as an incidental finding on physical examination. Cytologic findings in ultrasound‐guided fine‐needle aspirates of the mass were most compatible with a sarcoma, with abundant mineralized material and mixed inflammation. The mass was removed surgically and on gross examination was white‐tan, firm, associated with the mesentery, and when transected contained a gauze sponge in its center. On histopathologic examination, an area of central necrosis with mineralization and numerous refractile fibers consistent with sponge material was surrounded by dense fibrous connective tissue (gossypiboma). Within the connective tissue was a population of highly pleomorphic spindle cells consistent with a fibrosarcoma. Immunohistochemically, most neoplastic cells stained strongly positive for vimentin and a low number of cells were positive for smooth muscle actin. The results were consistent with a fibrosarcoma arising at the site of a retained surgical sponge. At a follow‐up visit 2 months postoperatively, ultrasonographic and cytologic evidence of metastasis was found in the spleen and mesentery. To our knowledge, this is the first report of malignant transformation at the site of a retained surgical sponge in a cat and the first report of a fibrosarcoma arising within a gossypiboma in a domestic animal.     

Extraskeletal osteosarcoma in two dogs

Extraskeletal osteosarcoma (ESOS) of the spleen and jejunum was diagnosed in 2 dogs. As an extremely uncommon type of tumor that has proven difficult to treat, ESOS is associated with high rate of local recurrence and metastatic disease. Extraskeletal osteosarcoma principally affects older dogs, has no apparent breed predilection, and may develop more frequently in males. The cause of ESOS is unknown, but may involve malignant metaplasia of pluripotential mesenchymal cells into osteoblasts. Macroscopically, ESOS usually is observed as a hard mass and may appear similar to calcified hematoma or myositis ossificans. The classic radiographic appearance of ESOS is a soft tissue mass with focal mineralization and without adjacent bone involvement.     

Migration of a retained surgical swab into the jejunum in a dog

A two‐year‐old spayed female shih‐tzu was referred with a 10‐month history of lethargy, chronic diarrhoea and weight loss. On presentation, a partial response to antibiotics was noted. Physical examination revealed an abdominal mass, and serum biochemistry and haematology revealed a mature neutrophilia, hypoalbuminaemia and a non‐regenerative anaemia. Contrast radiography and abdominal ultrasound were suggestive of an intraluminal foreign body. Exploratory laparotomy revealed a surgical swab in the lumen of the jejunum that was associated with severe adhesions. Histopathology showed evidence of transmural migration of the swab from the peritoneal cavity to the lumen of the jejunum.     

Extraskeletal osteosarcoma in the duodenum of a cat

A three-year-old, male neutered domestic longhair cat was referred for evaluation of icterus, vomiting, and anorexia. Abdominal ultrasonography revealed a proximal duodenal mass obstructing the common bile duct. The mass was surgically resected, and a cholecystoduodenostomy was performed. The histopathological diagnosis was osteosarcoma. Thoracic radiographs showed no evidence of metastasis, and bone scintigraphy revealed no signs of a primary skeletal osteosarcoma. Four months after surgery, the cat had intermittent vomiting, marked weight loss, and died.     

Extraskeletal osteosarcoma with pulmonary metastasis in a female f344 rat

A subcutaneous mass in the right femoral region of a female F344 Slc/N rat was examined histopathologically. At 83 weeks of age, the animal showed symptoms of severe anemia and nasal bleeding. Necropsy revealed that the mass had invaded the skeletal muscles but did not affect the bones. Multicentric nodules were also observed in the lung. Histopathology revealed a sheet-like growth pattern of polygonal tumor cells with round or comma-shaped nuclei and pale eosinophilic cytoplasm. Osteoid tissue was observed in not only the original lesion but also the metastatic foci in the lung. Each tumor cell was surrounded by argentophil fibers and few collagen fibers. Immunohistochemically, the tumor cells were positive for proliferating cell nuclear antigen (PCNA), vimentin, osterix and osteocalcin, but negative for keratin, S-100, von Willebrand factor, CD-31, CD-34, desmin, α-smooth muscle actin, lysozyme, α1-antitrypsin and rat malignant fibrous histiocytoma (MFH) antigen. CD-68-positive cells were considered to be infiltrated macrophages because they were negative for PCNA. On the basis of these findings, we diagnosed the present case as extraskeletal osteosarcoma.     

Extraskeletal fibroblastic osteosarcoma in a rabbit (Oryctolagus cuniculus)

A seven-year-old rabbit was presented with a non-painful mass in the right upper lip. Tissue samples from the mass at three different stages of the disease process were diagnosed sequentially as an osteogenic sarcoma, a fibroblastic tumour with rudimentary osteoid formation and, lastly, a fibrosarcoma. No bone involvement or metastatic disease was found. The final diagnosis was of an extraskeletal fibroblastic osteosarcoma, which is, to the authors' knowledge, the first reported such case in a domestic rabbit. Without the first two tissue samples, an incorrect diagnosis would have been reached; therefore, this disease may be underrepresented in the literature.     

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.     

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.     

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.     

Extraskeletal myxoid chondrosarcoma with systemic metastasis in a five-month-old irish setter dog

Extraskeletal myxoid chondrosarcoma was found in a five-month-old male Irish setter dog. At necropsy, the largest mass, measuring 15 × 13 × 13 cm, was found in the right caudal lobe of the lung, and metastatic small masses were observed in multiple organs. Microscopically, the tumor comprised mainly atypical mesenchymal cells and myxoid stroma, which stained positively with Alcian blue. Immunohistochemically, the tumor cells stained positively for vimentin, S-100 protein, neuron-specific enolase, calretinin, and chromogranin A. Ultrastructurally, the cytoplasm of the tumor cells was comprised abundant rough endoplasmic reticulum, mitochondria, Golgi complex, free ribosomes and short irregular microvillous processes extending from the cytoplasm. Based on these pathological findings, this tumor was diagnosed as extraskeletal myxoid chondrosarcoma.