Intracoelomic teratoma in a juvenile bald eagle (Haliaeetus leucocephalus).
Key words: teratoma, neoplasia, avian, bald eagle, Haliaeetus leucocephalus
A juvenile bald eagle that had been present at a warehouse in a light industrial area of Sitka, AK, USA, for a few days and was unable to fly was rescued by personnel from the Alaska Raptor Center. On physical examination, the bird was found to have a severely distended and soft abdomen. Other physical findings were loss of pectoral muscle mass, hypothermia, tachycardia, tachypnea, lime-green urates, and a heavy infestation of lice. Body weight was 3.8 kg (normal average weight for juvenile bald eagles of the northern subspecies is reported as 3.9 kg). (l) A heart murmur was present of variable intensity with sounds resembling cavitation. Skin turgor was normal. Presence of natal down remnants on some of the remiges confirmed it to be a 1-year-old bird. Its size was normal for a male bald eagle in this geographic region.
General anesthesia was induced with 5% isoflurane and oxygen delivered by face mask, then a 4-mm endotracheal tube was inserted and the bird was maintained on 1.5%-2% isoflurane at an oxygen delivery rate of 2 L/min with a nonrebreathing system. Spontaneous respiration under general anesthesia was shallow, so positive pressure ventilation was performed to ensure proper oxygenation. Whole-body radiographs in the ventrodorsal and lateral aspects were obtained, as well as a blood sample from the basilic vein. A 22-gauge intravenous catheter was placed in the right basilic vein for fluid support. The bird recovered slowly, but smoothly, from anesthesia.
On radiographs, the entire coelomic cavity was severely distended with soft tissue or fluid density. Loops of intestine could be visualized in the vicinity of the heart on the lateral view and no appreciable air sac volume remained. Differentiation of cardiac and hepatic silhouettes was not possible.
Results of initial blood tests showed a packed cell volume (PCV) of 14% with a total serum solids, measured by nontemperature-compensated refractometer, of 0.6 g/dl (reference range, 3.0-4.0 g/dl). (2) Blood samples for serum biochemical analysis, complete blood count (CBC), and serum electrophoresis were submitted for analysis (Comparative Pathology Laboratory, University of Miami School of Medicine, Miami, FL, USA) but were not available until after the case was resolved. Results of the CBC were within reference ranges, with the exception of anemia (PCV 14%; reference range, 37%-48%), leukopenia (9.9 x [10.sup.3] cells/[micro]l; reference range, 12-21 x [10.sup.3] cells/[micro]l, and absolute heteropenia (8.4 x [10.sup.3] cells/[micro]l; reference range, 8.8-13.5 x [10.sup.3] cells/[micro]l). (3) Abnormal serum biochemical values were low total protein (0.8 g/dl; reference range, 3.0-4.1 g/dl) (4) and high lactate dehydrogenase (5763 U/L; reference range, 252-340 U/L). (3) Results of serum protein electrophoresis revealed a low albumin concentration (0.3 g/dl; reference range, 1.4-1.8 g/ dl), low alpha-2 globulin fraction (0.02 g/dl; reference range, 0.29-0.69 g/dl), low beta globulin fraction (0.22 g/dl; reference range, 0.34-0.74), and low gamma globulin fraction (0.04 g/dl; reference range, 0.24-0.44 g/dl). (2)
Initial fluid support consisted of administration of 6% hetastarch (60 ml slow IV over 15 minutes) and 120 ml of 2.5% dextrose in 0.45% saline administered subcutaneously. Additional treatments were enrofloxacin (15 mg/kg SC; Baytril, Bayer, Shawnee Mission, KS, USA), furosemide (3 mg/kg IM once), vitamin B complex (2 mg/kg IM once), iron dextran (10 mg/kg IM once), and ivermectin (0.2 mg/kg IM once; Ivomec, Merck, Whitehouse Station, NJ, USA). Also, mite spray (pyrethrins 0.08%, piperonyl butoxide 0.3% topical once; Ultra-Care, 8 IN 1 Pet Products, Inc, Hauppauge, NY, USA) was applied lightly. The bird was placed in a cage and provided with supplemental heat. The plan was to perform a blood transfusion after a few hours of rest, but the eagle died in the subsequent hours.
At necropsy, a soft tissue mass approximately 13 cm in diameter was found occupying the coelomic cavity (Fig 1). This mass was attached to the left dorsolateral wall of the ventriculus and the mesenteric root. On sectioning, it contained variously sized spherical masses of tissue (Fig 2). Some resembled hepatic or splenic tissue in color and texture. Others contained crypts of mucus and sanguineous fluid. At the cranial pole, a region comprising smaller, yellow, horny nodules varied between 1 and 4 mm in diameter. On the basis of the gross findings, the mass was presumed to be a teratoma. The gastrointestinal tract and liver appeared normal, although severely displaced and smaller than usual, apparently because of compression. The spleen could not be located nor could the testes. The left lung had a brown lesion on its ventral aspect measuring 10 mm in diameter and penetrating 5 mm. The lesion was flush with the surface of the lung and did not grossly distort the parenchyma. The heart was small and pale. The right ventricle was enlarged and the right ventricular free wall was thin and flabby (one-sixth the thickness of the left ventricular wall). The kidneys were very dark brown. Samples of liver, heart, pancreas, gut, kidneys, lungs, skeletal muscle, and the intracoelomic mass were submitted for histopathologic examination.
[FIGURES 1-2 OMITTED]
Histopathologic results confirmed the diagnosis of teratoma. Tissues identified in the mass included cartilage, bone, lung, trachea, renal tubules, feather follicles, keratin cysts, nervous tissue, smooth muscle, and glandular epithelium resembling intestinal mucosa (Fig 3). The tumor was malignant, particularly the glandular portions that had infiltrated the serosal surfaces of many of the viscera and were associated with a schirrous response and adhesion formation. Other findings included atrophy of fat stores; pancreatic atrophy; mild periportal hepatitis with extramedullary hematopoiesis; hypertrophied interrenal cells in the adrenal gland consistent with stress; passive congestion of the lung; and congestion, hemorrhage, and compression atrophy of renal tissue. The source of the teratoma could not be determined.
[FIGURE 3 OMITTED]
Neoplasia is uncommonly reported in wildlife, especially in free-ranging raptors. We describe the first documented case of a teratoma in a raptor and only the second documented case of neoplasia in a bald eagle. Although teratomas can generally be treated successfully by surgical removal, this case demonstrates the need for early treatment.
Teratomas are tumors that consist of tissues arising from at least 2 embryonic germ layers. Often teratomas will contain tissues representative of endoderm, mesoderm, and ectoderm. (5) In the case presented here, all 3 germinal layers were represented. Endoderm was represented by lung and kidney tissue. Mesoderm was represented by cartilage, bone, smooth muscle, and nervous tissue. Ectoderm was represented by feather follicles, tracheal and intestinal mucosa, and renal tubular epithelium.
In wild birds, the incidence of neoplasia is considered to be low. (6) Only 1 previously documented case of neoplasia in a bald eagle has been reported. (7) One possible explanation for the low incidence of documented cases in wild birds is that those dying sporadically from nonepidemic conditions are seldom found and, thus, are underrepresented. (6) Teratomas have been documented in a variety of mammalian, reptilian, and avian species, including an African grey parrot (Psittacus erithacus erithacus), several species of ducks (Anas species), chickens (Gallus domesticus), domestic geese (Anser anser domesticus), ruffed grouse (Bonasa umbellus), old squaw (Clangula hyemalis), and Canada geese (Branta canadensis). (6,8) This was the first documented case of a teratoma in a raptor.
Generally, teratomas are not malignant, although they can grow to occupy enough space to interfere with function of adjacent organ systems and thus lead to death. This was demonstrated in this eagle by the compression atrophy of the lungs and kidneys and the severe displacement of the viscera. This teratoma was considered malignant because of its infiltration of the serosal surfaces of the ventriculus and other organs.
Teratomas are congenital, and possibly more than 1 mechanism can lead to their formation. Teratomas have been induced experimentally by injecting copper or zinc salts into the testes. (9) In one specific strain of mice, a genetic cause for the occurrence of teratomas has been suggested. (10) Abdominally located teratomas are the most common, and they generally arise from the gonads. (8,9) Although the exact tissue of origin could not be determined in this eagle, the teratoma possibly originated from testicular tissue because the testicles could not be located.
Teratomas should be considered a differential diagnosis for tumors in young birds. Diagnostic imaging could help confirm the location and extent of the tumor, but excisional biopsy is generally necessary for a definitive diagnosis. In humans, measurement of serum [alpha]1-fetoprotein and [beta]-human chorionic gonadotropin are helpful in diagnosis of germ cell tumors. (11,12)
Most teratomas are treated by surgical excision. If they are not malignant, surgical excision can be curative. (8) However, chemotherapeutic regimens, including combinations of bleomycin sulfate, cisplatin, vinblastine, ifosfamide, and etoposide, have been used in conjunction with surgery in the successful treatment of teratomas in nonavian species. (8,13,14) Regional deep heat therapy, delivered by an electromagnetic wave device, in combination with chemotherapy and surgical excision has also been used successfully in humans to treat malignant germ cell tumors, such as teratomas. (12) In this case, it is doubtful that surgical excision would have been successful given the malignant nature of the tumor and its size and degree of infiltration of several organs.
Although this case demonstrates what appears to be a common presentation of a teratoma in terms of location and tissue types, it is noteworthy because it is the first case reported in a raptor. Also, unlike most teratomas, this tumor was malignant. Lastly, the affected bird survived in the wild for approximately 1 year, allowing the teratoma to grow to a remarkable size before succumbing to the tumor.
Acknowledgments: We thank Drs Brian Speer and Drury Reavill for their assistance in this case.
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From the Alaska Raptor Center, 1000 Raptor Way, Sitka, AK 99835, USA (Ford); School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616, USA (Wentz); and Northwest ZooPath, 654 W Main Street, Monroe, WA 98272, USA (Garner). Present address (Ford): Medical Center for Birds, 3805 Main Street, Oakley, CA 94561, USA.
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|Title Annotation:||Clinical Report|
|Author:||Ford, Scott L.; Wentz, Sara; Garner, Michael|
|Publication:||Journal of Avian Medicine and Surgery|
|Article Type:||Clinical report|
|Date:||Sep 1, 2006|
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