Introduction

A Major Mitchell’s cockatoo (Lophochroa leadbeateri) of unknown age and sex was referred to the Exotic Animal Medicine Service, Veterinary Health Center at Kansas State University for closure of an open wound. The bird weighed 360 g, was purchased by the owner 3 weeks earlier, and housed in a 0.76 X 1.5-m cage separate from other birds in the home. The cockatoo was fed a mixture of commercial brand pellets, eating and drinking well, and behaving normally with no known history of trauma. An ulcerated mass, located caudodorsal to the cloaca at the base of the tail, was noted 3 days earlier by the referring veterinarian, who prescribed enrofloxacin (3 mg, PO, q 12 h).

Upon physical examination, a 2.0-cm-diameter, swollen lesion was noted. The tissue was ulcerated with crusting and purulent discharge, and the adjacent cloacal edges were reddened (Figure 1). The bird was bright, alert, and responsive and appeared otherwise healthy. Cytology from impression smears suggested spindle cell atypia with heterophilic-macrophagic inflammation. Complete blood count and plasma biochemistry results were unremarkable, and the bird was DNA-sexed as a male. The cockatoo was sent home on trimethoprim-sulfamethoxazole (50 mg/kg, PO, q 12 h for 10 days) and meloxicam (0.5 mg/kg, PO, q 12 h), pending diagnostics.

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Photograph of an ulcerated mass on the ventral tail of a Major Mitchell’s cockatoo (Lophochroa leadbeateri) at presentation.

Citation: Journal of the American Veterinary Medical Association 260, 12; 10.2460/javma.21.07.0335

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One week later, with the bird showing minimal clinical improvement, a CT scan and incisional biopsy were performed with the patient anesthetized. Anesthesia was mask-induced with 5% isoflurane prior to intubation with a 4-mm non-cuffed endotracheal tube and maintenance with 2% isoflurane delivered at 2-L/min oxygen flow rate. A 24-gauge IV catheter was placed in the right jugular vein, and a bolus of nonionic iodinated contrast agent (2 mL/kg, IV) was injected following the initial CT scan. The CT scan measured the soft tissue attenuating and mild contrast enhancing mass as 15.6 X 16.5 X 6.9 mm and revealed narrowing of the cloacal lumen. While the bird was anesthetized, two 4- to 5-mm wedge incisional biopsies were collected using a No. 15 scalpel blade and placed in formalin. Each surgical site was closed with a 5-0 absorbable suture. These biopsies showed fibroblastic proliferation interpreted as probable reactive fibroplasia but provided no definitive diagnosis. Trimethoprim-sulfamethoxazole and meloxicam were continued as before.

Because results for the incisional biopsy histopathology were inconclusive, 3 punch biopsies were collected under general isoflurane anesthesia 1 week later, and were again suggestive of reactive fibroplasia or a focal granuloma. Trimethoprim-sulfamethoxazole and meloxicam were continued. A week later (4 weeks from the initial presentation) the patient underwent surgical debulking. The morning dose of meloxicam was administered, and the patient was premedicated with ketamine (5 mg/kg, IM) in the pectoral muscle and once sedate, was mask induced with 5% isoflurane prior to being intubated with a 4 mm non-cuffed endotracheal tube and maintained on 2% delivered at a 2-L/min oxygen flow rate. A 24-gauge IV catheter was placed in the right jugular vein and lactated Ringer solution was administered at 10 mL/kg/h throughout the procedure. Anesthesia monitoring consisted of capnograph, ECG, and Doppler ultrasonic flow detector measurement of blood pressure.

The patient was positioned in dorsal recumbency on a heated surgical table, the feathers surrounding the mass and the tail feathers were completely removed and the area was aseptically cleaned. The surgical site was isolated using a clear surgical drape. A sterile cotton-tipped applicator was placed in the cloaca. The ulcerated mass was carefully excised using iris scissors, No. 15 scalpel blade, and blunt dissection. Hemostasis was performed using bipolar radiosurgery cautery. The deep tissues were apposed using a 4-0 absorbable suture in a simple interrupted pattern and the skin was apposed using the same suture material with a cruciate pattern. Meloxicam (0.5 mg/kg, IM) was given prior to recovery, which was uneventful. The patient was monitored for changes in mentation, behavior, appetite, or stools throughout recovery and no changes were noted. The patient was discharged the following day with meloxicam (0.5 mg/kg, PO, q 12 h), amoxicillin–clavulanic acid (120 mg/kg, PO, q 12 h), and enrofloxacin (30 mg/kg, PO, q 24 h), pending test results. The owners were encouraged to keep a provided e-collar on the patient to prevent further trauma to the surgical site and monitor for behavioral changes that could indicate pain. The resected mass was placed in formalin and submitted for histopathologic evaluation, which revealed that the previously observed spindle cell proliferation was highly infiltrative and less organized on the deep margins supporting the diagnosis of a soft tissue sarcoma. The diagnosis of fibrosarcoma was determined by trichrome staining which demonstrated more extensive collagen deposits and infiltration on the deeper margins indicating an incomplete surgical excision of the mass (Figure 2).

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Photomicrograph of a section of the fibrosarcoma in the cockatoo of Figure 1 at 4X magnification showing extensive collagen deposits (blue staining) and infiltration into the surrounding skeletal muscle (red-stained cells) at the deep margins. Trichrome stain; bar = 100 µm.

Citation: Journal of the American Veterinary Medical Association 260, 12; 10.2460/javma.21.07.0335

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The patient was examined again 3 weeks after surgical debulking (7 weeks from the initial presentation). The bird had been eating and drinking well, behaving normally, and maintained normal body weight but the mass had regrown with multiple scabs and repeated bleeding.

In consultation with the Oncology Service, Veterinary Health Center at the Kansas State University, a postoperative definitive radiation therapy protocol was developed. The cockatoo was mask-induced with 5% isoflurane prior to being intubated with a 4 mm non-cuffed endotracheal tube and maintained on 2% delivered at a 2-L/min oxygen flow rate, and placed in dorsal recumbency for all radiation procedures. The radiation treatment field was manually set to include the mass and margins based on palpation under anesthesia immediately before the first dose of radiation therapy. A linear accelerator (Clinac 2100C/D; Varian Medical Systems) was used to deliver 3 Gy once daily for 20 fractions, Monday through Friday, resulting in a total accumulative dose of 60 Gy. A single electron beam (20 MeV, 6 cm X 6 cm electron cone) in 100 cm source-to-skin distance (SSD) setup was used to prescribe 3 Gy/fraction to the 93% isodose line covering the entire thickness of the tail base below the cloaca. Each treatment session took 15 to 20 minutes in total, and recovery was uneventful in all instances. By the completion of radiation therapy (12 weeks from the initial presentation), the lesion had decreased in size with contracted wound edges, but still contained dried necrotic debris on its surface. The surrounding tissue within the irradiated field appeared normal and no adverse reactions to the radiation therapy were observed. At a follow-up appointment 2 weeks after treatment completion the lesion had further decreased in size with contracture of the wound edges and a dried scab present. The rest of the physical examination was unremarkable.

Follow-up phone checkups reported no obvious issues. On physical examination 6 months after treatment completion the lesion appeared completely healed with no sign of reoccurrence. The bird weighed 385 g (an increase of 25 g from the original presentation), was in good body condition, and the physical examination was unremarkable. Complete blood count and plasma biochemistry results were unremarkable. The owners were instructed to schedule a follow-up appointment in another 6 months and to monitor for any signs of reoccurrence. As of 1.5 years posttreatment the owner reported no signs of reoccurrence.

Discussion

This case report describes the diagnosis and treatment of fibrosarcoma in a Major Mitchell’s cockatoo. Fibrosarcomas are locally invasive malignant neoplasms of fibrous tissue classified as a type of soft tissue sarcoma,^1,2 and have been rarely reported to metastasize in birds.^1,3,4 A survey of 1,539 cases of neoplasia in pet birds found soft tissue neoplasms to be the most common at 31.7%,⁵ indicating the need for establishing effective treatment protocols for such cases.

Wide excisional margins involving tail amputation was initially considered in this case, as complete surgical resection is the recommended treatment for localized masses.⁶ Successful avian tail amputation to achieve excisional margins of a uropygial gland adenocarcinoma has been reported.⁷ However, this patient was not a candidate for amputation with wide excisional margins due to the narrowing of the cloacal lumen identified on CT caused by the proximity of the mass. Surgical resection in this case would likely result in compromise of the cloaca.

The patient received oral meloxicam throughout the diagnostic period for pain management at 0.5 mg/kg every 12 hours, derived by splitting a psittacine recommended dose of 1 mg/kg every 24 hours^8,9 into twice daily administration. Ketamine was used as premedication for the surgical debulking procedure to assist in analgesia. The patient responded favorably to meloxicam alone postoperatively as evidenced by normal mentation, behavior, appetite, and stools. Studies^10,11 in other species have shown that NSAIDs may be effective in controlling severe pain, such as from orthopedic surgery, when given without an opioid. However, if patient response had indicated a need for increased pain management, an opioid or other pain medication may have been incorporated.

After consultation with the oncology service, a course of definitive radiation therapy was elected for long-term control. Previous reports include a fibrosarcoma in a blue and gold macaw (Ara ararauna) treated with orthovoltage radiotherapy at a total of 44 Gy, divided into 4 Gy X 11 fractions, which was combined with the addition of intratumoral cisplatin during 2 of the treatments.¹² Another report of fibrosarcoma in a blue and gold macaw used orthovoltage radiotherapy at a total of 40 Gy, divided into 4 Gy X 10 fractions combined with intratumoral cisplatin during 3 of the treatments.¹³ Possible adverse effects of radiation therapy may include acute toxicity such as mucositis and skin irritation and/or delayed toxicity such as fibrosis and bone necrosis.¹⁴ Specific concerns are highest for the cloacal mucosa, uropygial gland, urogenital, and intestinal systems due to the anatomic location of the lesion. Radiation doses up to 72 Gy total resulted in no adverse effects other than minimal epidermal changes in a study of ring-necked parakeets (Psittacula krameri).¹⁵ For the cockatoo of the present report, a prescription of 60 Gy given as 20 X 3 Gy fractions was elected to deliver conventional fractionation for definitive intent, the standard approach in dogs.¹⁶ Repeated intubations required for radiation therapy may increase the risk of tracheal mucosa damage, fibrosis, and eventual tracheal stenosis, especially due to the complete tracheal rings present in avian patients. This risk is reduced by the use of an uncuffed endotracheal tube as was done in this case.¹⁷ This patient tolerated all anesthetic events and radiation doses well with the only notable side effect being temporary superficial necrosis of the epidermal layer of the targeted mass, which is expected during radiation treatment.

No chemotherapeutic agents were used in the treatment of this cockatoo. The previous reports^12,13 of avian fibrosarcoma treated with radiation therapy also concurrently administered intratumoral cisplatin with no reported significant adverse effects. Possible adverse effects of cisplatin include myelosuppression, gastrointestinal toxicity, nephrotoxicity, and ototoxicity.¹⁸ Pharmacokinetic studies of intravenous cisplatin in sulfur-crested cockatoos (Cacatua galerita) highlight the risk of nephrotoxicity at higher doses.^19,20 However, intratumoral cisplatin has been used in the treatment of other neoplasms in avian species with varying success and no reported adverse effects.^21,22 Although it appears that intratumoral administration of cisplatin produces fewer adverse effects than intravenous administration, the use of cisplatin was avoided in the cockatoo of the present report because of its unknown benefit.

Surgical debulking followed by radiation therapy alone appeared to provide definitive diagnosis and treatment in this patient while maintaining the tail function and cosmetic appearance. The total radiation dose of 60 Gy used in this case is higher than doses prescribed in previously reported similar avian cases.^12,13 However, no significant adverse responses were observed in this case, and the mass was reduced in size by the completion of radiation treatments and appeared completely healed with no signs of reoccurrence at 18 months post treatment. The experience from this case suggests that this protocol can be a viable option and safe treatment for avian fibrosarcoma.