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Synovial sarcoma associated with indwelling intramedullary pin in a peach-faced lovebird (Agapornis roseicollis).

Abstract: Sarcoma developing in association with a metallic orthopedic procedure is an uncommon but well-recognized complication in mammals. We report on a synovial sarcoma that developed at the site of an intramedullary pin after surgery to treat a bone fracture. A 17-year-old female peach-faced lovebird (Agapornis roseicollis) developed a spherical mass on the distal right dorsal wing at a site that was previously fractured and surgically repaired with an indwelling intramedullary pin. The right wing was amputated at the scapulohumeral joint. One year later, the bird died. Postmortem examination revealed metastases in the right lung, left thoracic wall, and proventricular serosa. Histologically, the tumor had a characteristic biphasic pattern. The tumor was immunohistologically and ultrastructurally identified as a synovial sarcoma. This is the first report of a suspected fracture-associated sarcoma in a bird.

Key words: synovial sarcoma, fracture-associated sarcoma, intramedullary pin, air sac metastasis, avian, lovebird, Agapornis roseicollis

Clinical Report

A 17-year-old female peach-faced lovebird (Agapornis roseicollis) was examined because of swelling and signs of pain in the distal right dorsal wing. A spherical mass measuring approximately 1.5 cm in diameter was identified at the cubital region of the right proximal humerus. Two years earlier, a bone fracture at the same site was surgically repaired with an intramedullary pin, which remained implanted at the site.

Radiographs revealed osteolysis surrounding the pin and a circular radiopaque structure measuring approximately 6 mm in diameter in the right lung (Fig 1), although no respiratory signs were observed. One week after the initial examination, the pin was observed protruding from the mass and was easily and successfully removed. However, 1 week later, the mass increased in size and became lobulated. Subcutaneous emphysema was also detected, which was attributed to air leakage from the pneumatic bone (Fig 1, inset). The right wing was amputated at the scapulohumeral joint, and the bird recovered well after surgery. However, 1 year after the amputation, the bird developed acute onset hemoptysis and died. Radiographs taken 4 months before the bird's death did not show any change in the size of the radiopaque lesion in the right lung. There were no signs of tumor recurrence at the site of the wing amputation.

On macroscopic examination of the right dorsal wing at the time of amputation, the mass was solid and lobular, measuring approximately 2 X 1.5 cm, with irregular surfaces and translucent yellow to gray-white. The mass extended from the elbow to the shoulder joint, with destruction of the articular surfaces of the elbow joint. However, the mass did not appear to involve the humeral head, body wall, radius, or ulna.

At postmortem examination, a massive dark red and green blood clot was identified extending from the left lung to the left posterior thoracic air sac and left abdominal air sac. No macroscopically visible structure was identifiable as the left lung. A gray-white membranous tissue covered the left surface of the blood clot near the tracheal bifurcation and extended onto the esophagus and left bronchus (Fig 2A). A translucent white tissue covered the entire inner surface of the left thoracic wall and distended the intercostal nerve at the blood clot site (Fig 2B). The right lung contained 2 white masses: one mass on the visceral surface measuring approximately 2x4 mm and one mass on the dorsal surface measuring approximately 5 mm in diameter (Fig 2C). A spherical mass measuring approximately 5 mm in diameter was found on the abdominal side of the proventricular serosa.


Histopathologic examination was performed at the time of amputation of the right wing and at the time of postmortem examination. Tissue sections, including the neoplastic mass, were fixed in 10% phosphate-buffered formalin. The mass including the bone was decalcified with K-CX (Falma Corporation, Tokyo, Japan). The tissues were embedded in paraffin and sectioned at approximately 4 (Vim for hematoxylin and eosin, Watanabe's silver impregnation, and immunohistochemical staining (primary mouse monoclonal antibodies to vimentin [Vim 3B4. DakoCytomation Denmark A/S, Glostrup, Denmark] and human cytokeratin [AE1/AE3, Dako North America Inc, Carpinteria, CA, USA]). For electron microscopy, the solid proliferative area of the right wing mass was sectioned from the paraffin block into 1-[mm.sup.3] slices. The sections were deparaffinized, processed routinely, and embedded in epoxy resin. Ultrathin sections were prepared and stained with uranyl acetate and lead citrate.

Histologic examination of the right wing revealed the neoplastic tissue had proliferated throughout the entire humerus except for the humeral head, destroying the bone and infiltrating into the medullary cavity. The tissue was biphasic and primarily comprised histiocyte-like oval to spherical cells in a solid structure. Spindle cells in a solid and bundle growth pattern were also present in some sites (Fig 3). The surface of the mass was covered with papillomatous proliferative cells bordered by epithelial-like cells (Fig 4), with both cell types showing a high rate of mitotic figures. Cleft-like spaces and glandular structures were present throughout the mass, as were transitional forms of both structures (Fig 5).

The membrane-like tissue on the left surface of the blood clot was identified as the left lung, with no neoplastic tissue identified. Proliferative cells in the tissue that covered the entire dorsal surface of the left thoracic wall and those in the 2 masses in the right lung and the proventricular mass were identical to the neoplastic cells in the right dorsal wing. Results of Watanabe's silver impregnation stain showed the proliferative spindle cell regions comprised well-developed argentophilic fibers surrounded by individual tumor cells. These argentophilic fibers were virtually absent within the alveolar configuration. Additionally, the basal membranes of the glandular structures were discontinuous and indistinct.

On immunohistochemical testing, most neoplastic cells were positive for anti-vimentin antibodies, and the cells forming the glandular cavities and those bordering the tumor margins were positive for anti-cytokeratin antibodies. In the solid growth area of the tumor, some cytokeratin-positive cells that had not yet formed a lumen were present (Fig 6). Some immunohistochemical overlap was observed between the vimentin and cytokeratin areas (Fig 7).


Ultrastructural examination revealed an incomplete lumen formed by neoplastic cells that was lined by cells with microvilli. These cells were connected by a cell adhesion structure and had a discontinuous basal membrane (Fig 8).


In mammals, sarcoma developing in association with a metallic orthopedic implant is an uncommon but well-recognized complication. Intramedullary pinning of bone fractures is the most common orthopedic procedure in birds, but it is rare to leave an indwelling pin in place for a prolonged period. In addition to other potential adverse effects in birds, an indwelling pin increases the body weight. In this report we describe the development of synovial sarcoma at the site of an indwelling pin after surgery to treat a bone fracture in a lovebird.



Synovial sarcoma is a rare type of malignant soft tissue tumor but has been reported in dogs, (1,2) cats, (3) sheep, (4) cattle, (5,6) and birds. (7-9) Three cases of synovial sarcoma have been reported in birds, including a Moluccan cockatoo (Cacatua moluccensis), (7) a pigeon, (8) and a sulphur-crested cockatoo (Cacatua galerita). (9) In all cases, the disease appeared as a single mass on the wing. The present case was diagnosed as a synovial sarcoma because the tumor had properties consistent with those described by the World Health Organization (WHO) classification for synovial sarcomas. (10,11) These properties include severe destruction of the elbow joint, a biphasic pattern with nonepithelial and epithelial-like components and a few tumor cells with both vimentin and cytokeratin, and a defective basal membrane on electron microscopy. In this bird, the primary tumor site was believed to be the right elbow joint along the dorsal wing, based on the tumor size, distribution, the extent of destruction in the surrounding tissue, and the radiographic findings over time. The metastasis to the right lung likely occurred by the hematogenous route; however, the metastatic pattern in the left thoracic wall and proventricular serosa suggested that the tumor spread via the interclavicular air sac. Evidence for spread via the air sac included both clinical and histologic findings: before wing amputation, subcutaneous emphysema was detected and was attributed to air leakage from the affected pneumatic bone; no tumor cells were present at the site of the wing amputation; the parenchyma of the left lung did not have a metastatic mass; and the tumor tissue infiltrated between the left lung and the dorsal wall of the thorax. This is regarded as invasion from the air sac. (12,13) In people, aerogenous dissemination is observed only in the lungs. However, birds have air sacs, and a metastasis may spread from the air sacs into the abdominal cavity as well as to the lungs. In people, placement of orthopedic implants to repair bone fracture has been associated with the development of sarcoma. (14) Fracture-associated sarcoma has also been reported in dogs, (15,16) goats, (17) and cats. (18,19) In cats and dog, fibrosarcomas associated with microchips have been reported as well. (20-22) The relationship between traumatic injury and synovial sarcoma has not been elucidated. However, reports of human cases have demonstrated a history of traumatic injury from several weeks to as long as 40 years before the onset of disease at synovial sarcoma sites. (23-25)


Intramedullary pinning of bone fractures is the most common orthopedic procedure in birds; however, to avoid an increase in body weight, the indwelling pin is rarely left in place. In this case, the bird suffered a bone fracture 2 years earlier that was treated with an indwelling pin. Therefore, we suspect that in the bird we describe in this report, the indwelling pin may have played a role in inducing the tumor. For orthopedic procedures in pet birds, leaving an indwelling pin in place for longer than necessary should be avoided.




Yumiko Nakano, DVM, and Yumi Une, DVM, PhD

From the Nakano Bird Clinic, 3-35-10 Wakamiya, Nakanoku, Tokyo 165-0033, Japan (Nakano); and the Laboratory of Veterinary Pathology, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan (Nakano, Une).

Acknowledgments: We thank Atsushi Kojima, DVM, who performed a complete amputation of the bird's right wing.


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Title Annotation:Clinical Report
Author:Nakano, Yumiko; Une, Yumi
Publication:Journal of Avian Medicine and Surgery
Article Type:Clinical report
Date:Mar 1, 2016
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