Fibrosarcoma in a Maned Wolf (Chrysocyon brachyurus)
American Association of Zoo Veterinarians Conference 1999
Erin E. McNulty1, DVM; Stephen D. Gilson2, DVM, MS, DACVS; B. Scott Houser3, DVM; Andrea Ouse4, MS
1Brown Road Animal Clinic, Mesa, AZ, USA; 2Sonora Veterinary Specialists, Phoenix, AZ, USA; 3Mobile Practice, Litchfield Park, AZ, USA; 4Wings Southwest, New River, AZ, USA

Abstract Case Report

A 12-yr-old 27-kg intact male maned wolf (Chrysocyon brachyurus), while in his habitat display, was noted to have a mass on the lateral upper lip, below the left nare. Housed with a mate at the Wildlife World Zoo for 7 yr, both had received annual physical examinations, CBC, chemistry profile, serology testing for coccidioidomycosis, heartworm and Ehrlichia canis and vaccinations (Duramune KF-11, Fort Dodge Laboratories, Inc., Fort Dodge, Iowa, USA; 1 ml s.c.; Galaxy-D, Solvay Animal Health, Inc., Mendota Heights, Minnesota, USA; 1 ml s.c.; and ImRab 3, Rhone Merieux, Inc., Athens, Georgia, USA; 1 ml i.m.). The affected maned wolf had had no previous abnormalities.

The wolf was anesthetized with 100 mg tiletamine/zolazepam (Telazol, Fort Dodge Laboratories, Inc., Fort Dodge, Iowa, USA; 1 ml i.m.) by blowpipe (Telinject, Saugus, California, USA), intubated, and maintained on isoflurane and oxygen anesthesia. On oral examination a 5x2.5x2 cm mass was noted on the rostral maxilla. It was a lobular, nodular, raised, pink-gray soft tissue mass, with an ulcerated lesion on one side. Two lateral incisors were incorporated into the mass and were loose. The mass was debulked, removing the affected incisors, and samples were submitted for histologic evaluation. Maxillary radiographs revealed osteolysis in the affected area, up to, but not including the associated maxillary canine tooth. The wolf was given 1.2 mg butorphanol (Torbutrol, Fort Dodge Laboratories, Inc., Fort Dodge, Iowa, USA; 0.6 ml i.v.). Blood was drawn for CBC, chemistry, heartworm antibody testing, coccidioidomycosis antibody testing and Ehrlichia antibody testing. The wolf awoke from anesthesia uneventfully.

The hemogram abnormalities included (Table 1) decreased hemoglobin, hypochromia and decreased platelets. Serum chemistry abnormalities included (Table 1) an elevated blood urea nitrogen, decreased alkaline phosphatase and decreased amylase. The agar gel immunodiffusion test for coccidioidomycosis, the enzyme-linked immunosorbent assay test for heartworm, the indirect florescent antibody test for Ehrlichia canis were all negative. On histologic analysis the rostral maxillary mass was diagnosed as a low-grade fibrosarcoma. There were interdigitating whorls, bundles and fascicles of spindle cells intersecting at various angles. Vessels showed a large area of thrombosis. There were only occasional mitotic figures seen.

Table 1. Abnormal hematologic and serum biochemical findings in a maned wolf



ISIS meana

Hemoglobin (g/dl)



Mean corpuscular hemoglobin concentration (g/dl)



Platelets (k/mm3)



Blood urea nitrogen (mg/dl)



Alkaline phosphatase (IU/L)



Amylase (IU/L)



aInternational Species Information System, Apple Valley, Minnesota, USA

Five weeks later, the maned wolf was referred for a rostral maxillectomy. The wolf was anesthetized with 140 mg tiletamine/zolazepam by blowpipe, intubated and maintained on isoflurane and oxygen anesthesia. Examination of the affected area revealed regrowth of the mass, to approximately 0.3x0.2 cm size. Presurgical maxillary radiographs revealed no progression of the osteolysis from previous radiographs. Thoracic radiographs were normal. An indwelling catheter was placed in the left cephalic vein, and 950 ml normosol (Normosol-R, Abbott Laboratories, North Chicago, Illinois, USA) was administered during the course of anesthesia. Additional drugs administered were 1 g cefazolin (Cefazolin, Marsan Pharmaceuticals, Inc., Cherry Hill, New Jersey, USA) and morphine (Morphine Sulfate Injection, Elkins-Sinn, Cherry Hill, New Jersey, USA). Blood pressure was monitored using a doppler (Ultrasonic Doppler Flow Detector, Parks Medical Electronics, Inc., Aloha, Oregon, USA). The maxillectomy was routine, incorporating both maxillary canine teeth. Post-surgically a 75 µg/hr fentanyl patch (Duragesic Fentanyl Transdermal System, Janssen Pharmaceutica, Inc., Titusville, New Jersey, USA) was placed between the shoulder blades. The wolf awoke from anesthesia uneventfully. The entire rostral maxilla was submitted for histologic analysis.

Histopathologically, the mass was a low-grade fibrosarcoma. The sample was characterized by interdigitating whorls, fascicles and palisades of spindloid tissue, with a mitoses range from 1–2/hpf. Resection margins were histologically complete.

The wolf recovered well, and began to eat the day following surgery. The fentanyl patch fell off 4 days following surgery. Nineteen days following surgery, the wolf was anesthetized with 100 mg tiletamine/zolazepam (Telazol, 1.0 ml i.m.) by blowpipe, and supplemented with 50 mg ketamine (Ketaset, Fort Dodge Laboratories, Inc., Fort Dodge, Iowa, USA; 0.5 ml i.m.). Oral examination showed the sutures to be in place, the incision healing well and no evidence of tumor regrowth.

Twenty-nine weeks following maxillectomy, the wolf was noted to be ataxic, dyspneic and weak. The wolf was anesthetized with 100 mg tiletamine/zolazepam (Telazol, 1.0 ml i.m.) by pole syringe (Telinject, Saugus, California 91350 USA). The wolf’s weight was 25 kg. On oral examination there was a left lateral mass extending from the upper lip mucosa to the maxilla. Due to the likely recurrence of the fibrosarcoma, and the wolf’s old age, the wolf was euthanatized using sodium pentobarbital (Beuthanasia-D Special, Schering-Plough Animal Health Corp., Kenilworth, New Jersey, USA).

A complete necropsy showed generalized atrophy of the skeletal musculature. There was a hepatic cystic mass on a single surface, with pale foci throughout the liver. The jejunal mucosa appeared inflamed. There was a 2,858-g mediastinal tumor adhered to one lung lobe. All lung lobes had encapsulated fibrous masses throughout the parenchyma. Histopathologically, there was centrolobular degeneration in the liver, with infiltrations of some erythrocytes suggesting some focal hemorrhages. The kidney glomeruli appeared normal, but the tubules had varying degrees of degenerative changes (many were vacuolated and others were granular). This appeared to be a terminal nephrosis of undetermined cause. The rostral maxillary, mediastinal and lung masses were all well-differentiated fibrosarcomas. All contained a measurable amount of bundles and sheets of spindle-shaped cells with some collagen formation.


The maned wolf described in this report had a fibrosarcoma that acted very similarly to that found in the domestic dog. The original rostral maxillary mass grew back aggressively after the original biopsy. Presurgical thoracic radiographs did not show any metastases. A rostral maxillectomy was performed, with margins determined to be clean. The wolf recovered uneventfully from the surgery and did well for 7 mo. Because of his age and low reproductive status, it was decided not to perform further treatment should the tumor recur. Subsequently, we performed only visual examinations to ensure the wolf’s comfort and clinical status. It was not known exactly when the fibrosarcoma began to regrow on the upper lip. When the wolf did finally depict clinical signs of dyspnea and weakness, the local recurrence and lung metastases were severely aggressive.

Due to the wolf’s status as an endangered species, the authors feel the initial aggressive surgical option was warranted. Follow-up reevaluations and perhaps future surgeries might also be warranted in a younger maned wolf that is more valuable to the present gene pool of captive specimens.


Speaker Information
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Erin E. McNulty, DVM
Brown Road Animal Clinic
Mesa, AZ, USA

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