History
A 13-year-old 24-kg (52.8-lb) sexually intact female red kangaroo (Macropus rufus) was evaluated because of a 1-day history of mild ataxia, lethargy, and increased expiratory effort. Appetite was considered normal, but there had been weight loss of 5.5 kg (12.1 lb) over a 5-month period. Five months prior to the evaluation, the kangaroo had been immobilized for routine melengestrol acetate implantation; no abnormalities were evident at that time.
Clinical and Cytologic Findings
The kangaroo was immobilized for the evaluation with ketamine and medetomidine, and anesthesia was maintained with isoflurane and oxygen. Thoracic auscultation revealed occasional wheezes and muffled and harsh lung sounds. The sclera of each eye was markedly icteric. A CBC and serum biochemical analysis revealed icteric serum and marked hyperbilirubinemia (8.7 mg/dL; reference range, 0.0 to 0.4 mg/dL), hypoalbuminemia (1.2 g/dL; reference range, 3.3 to 4.7 g/dL), hypoproteinemia (4.4 g/dL; reference range, 5.4 to 7.4 g/dL), and mild leukocytosis (7.3 × 103 leukocytes/μL; reference range, 3.17 × 103 leukocytes/μL to 6.75 × 103 leukocytes/μL). Thoracic radiography revealed a diffuse interstitial nodular lung pattern, which was more concentrated in the dorsal pulmonary fields.
A tracheal wash was performed. Aspiration yielded serosanguineous fluid and blood clots. Evaluation of cytologic specimens in-house identified numerous RBCs, occasional WBCs, and rare epithelial cells. Samples of the fluid were submitted for further cytologic examination at a diagnostic laboratory.a
Direct smear preparations of the tracheal wash fluid were stained with Romanowsky stain. On microscopic examination, the smears contained moderate numbers of atypical epithelial cells, scattered mature ciliated columnar epithelial cells, and occasional leukocytes in a background of blood (Figure 1). The atypical epithelial cells were present in tightly cohesive, disorganized clusters with crowded nuclei. These cells were poorly differentiated, ranged from 15 to 30 μm in diameter, and had a high nuclear-to-cytoplasmic ratio. Nuclei were round to oval and had moderate to marked anisokaryosis. Some cells had prominent elongated nucleoli. Cytoplasm was scant and deeply basophilic.
Photomicrograph of cells in direct smears of tracheal wash fluid (A) obtained from and photograph of the lungs, liver, and gallbladder (B) in a red kangaroo (Macropus rufus) that was evaluated because of a 1-day history of mild ataxia, lethargy, and increased expiratory effort. In panel A, notice the clusters of epithelial cells that are large, present in a disorganized arrangement, and have a high nuclear-to-cytoplasmic ratio and marked anisokaryosis. Aqueous Romanowsky stain; bar = 20 μm. Inset—Cluster of normal mature ciliated columnar epithelial cells for comparison. Aqueous Romanowsky stain; bar = 10 μm. In panel B, there are multifocal to coalescing, variably sized, pale, bulging nodules within the lungs (black arrow) and liver (white arrow). The gallbladder is distended (asterisk).
Citation: Journal of the American Veterinary Medical Association 243, 2; 10.2460/javma.243.2.221
Anesthesia was reversed with atipamezole, and the kangaroo had a prolonged recovery. The next day, the kangaroo's condition improved slightly and it was eating, drinking, urinating, and defecating normally; however, it died in the afternoon. A complete gross necropsy was performed. Disseminated throughout the lungs were multifocal to coalescing, variably sized, pale, firm, and bulging nodules (Figure 1). The centers of larger nodules were dark and necrotic. The liver contained similar nodules throughout all lobes. The gallbladder and bile duct were markedly distended and could not be manually expressed. A nodule (1 cm in diameter) similar to those described was found in the pancreas and was the cause of the biliary obstruction. Once the bile duct was severed proximal to the nodule, the gallbladder was easily expressed and appeared grossly normal. The left adrenal gland appeared irregular with loss of normal cortex and medullary demarcation. The remainder of the postmortem examination revealed no remarkable findings.
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page →
Histopathologic Findings
Representative samples of the pancreas, lungs, liver, and intestinal tract were fixed in 10% formalin for histologic evaluation. The tissues were routinely processed and stained with H&E stain. Within the pancreas and arising from the ductal region were large, multifocal neoplastic nodules composed of tubules and clusters supported by a fine fibrous stroma (Figure 2). The adjacent unaffected pancreatic ducts were markedly hyperplastic. Similar neoplastic nodules were scattered throughout the lungs and liver. The neoplastic cells were cuboidal with a moderate amount of amphophilic cytoplasm and indistinct cell borders (Figure 3). The nuclei were round to oval with clumped chromatin and often contained 1 to 2 nucleoli. In sections of the pancreas, there were 9 mitotic figures in 10 hpfs; there were similar findings in the sections of the neoplastic areas of the lungs and liver. Clusters of neoplastic cells were present within the blood vessels in the lungs and small intestine. The left adrenal gland also contained similar neoplastic cells.
Photomicrographs of tissue sections obtained from the kangaroo in Figure 1 to illustrate the invasive nests of neoplastic epithelial cells that infiltrated and obliterated the pancreas (A), marked hyperplasia within some of the pancreatic ducts (B), and neoplastic nodules in the lungs (C) and liver (D) composed of tubules and clusters supported by a fine fibrous stroma. Normal tissue is denoted by asterisks. H&E stain; bar = 500 μm.
Citation: Journal of the American Veterinary Medical Association 243, 2; 10.2460/javma.243.2.221
Photomicrograph of a section of liver obtained from the kangaroo in Figure 1. Notice the neoplastic cells composed of tubules and clusters supported by a fine fibrous stroma. The neoplastic cells have indistinct cell borders, and the nuclei are round to oval with clumped chromatin. H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 243, 2; 10.2460/javma.243.2.221
Cytologic and Histologic Diagnosis and Case Summary
Cytologic and histologic diagnosis: neoplastic nodules present in the lungs and liver.
Case summary: metastatic adenocarcinoma in a red kangaroo.
Comments
On the basis of the gross, cytologic, and histopathologic findings for the kangaroo of this report, a diagnosis of metastatic adenocarcinoma was made. The tissue of origin could not be definitively determined owing to the extent of pathological changes in multiple tissues and lack of differentiation of the neoplastic cells. It was presumed that given the extensive involvement of the common bile duct detected grossly and the pancreatic ducts detected histologically, one of these locations served as the primary origin of the neoplasm. The clinical signs and examination findings were consistent with this diagnosis.
The kangaroo was evaluated because of a 1-day history of mild ataxia, lethargy, and increased expiratory effort; although clinical signs were mild, it died shortly after initial evaluation. In patients with pulmonary neoplasia, transthoracic needle aspiration of lesions identified via diagnostic imaging is considered more likely to yield diagnostic samples than does respiratory tract washing.1,2 However, as in the case described in this report, examination of tracheal wash samples may result in a definitive diagnosis if neoplastic cells have invaded the bronchial tree and are available for collection. Therefore, tracheal washing may be a valuable diagnostic tool when radiographic changes in the lungs are similar to those detected in the kangaroo of this report.
Common causes of death among macropods are rarely reported in the literature, and only a small subset are related to neoplastic diseases.3–8 In a retrospective study7 of deaths among captive kangaroos, diseases of the alimentary tract were the most common, followed by pneumonia and disseminated toxoplasmosis. Only 1 animal had neoplastic disease in that study.7 In other studies5,8 that investigated neoplastic disorders in captive red kangaroos, the incidences of mammary gland adenocarcinomas and oral squamous cell carcinomas were the highest, even though few animals were affected. Pre- and postmortem examinations of the kangaroo in this report did not reveal any gross abnormalities in the mammary glands or oral cavity; thus, tissues from those areas were not submitted for histologic examination. The true incidence of neoplastic disorders in species of macropods is unknown because not all cases are reported. Regardless of the reported incidence, neoplasia needs to remain on the differential diagnoses list for these described clinical and radiographic signs in macropod species.
Antech Diagnostics, Stillwater, Okla.
References
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4. Canfield PJ, Hartley WJ. A survey and review of hepatobiliary lesions in Australian macropods. J Comp Pathol 1992; 107: 147–167.
5. Canfield PJ, Hartley WJ, Reddacliff GL. Spontaneous proliferations in Australian marsupials—a survey and review. 1. Macropods, koalas, wombats, possums and gliders. J Comp Pathol 1990; 103: 135–146.
6. Speare R, Banks D. A trichoepithelioma in a wild eastern grey kangaroo (Macropus giganteus). J Wildl Dis 1987; 23: 508–509.
7. Stern AW. A retrospective study of disease in captive kangaroos from Oklahoma State University, 1995–2009. J Vet Diagn Invest 2010; 22: 324–326.
8. Suedmeyer WK, Johnson G. Survey of neoplasia in red kangaroos (Macropus rufus), 1992–2002, in a zoological collection. J Zoo Wildl Med 2007; 38: 231–239.
