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Infraorbital Keratin Cyst in an Umbrella Cockatoo (Cacatua alba).

Abstract: A 10-year-old, female umbrella cockatoo (Cacatua alba) was presented for evaluation of a mass at the right commissure of the beak, with associated right periorbital swelling. A feather cyst was suspected, based on history and the results of a computed tomography scan and fine-needle aspirate. The cyst was surgically debrided and removed. Histopathologic results confirmed an infraorbital keratin cyst, most likely originating from a feather follicle. To our knowledge, this is the first reported case of a periorbital keratin cyst in a bird.

Key words: feather cyst, keratin cyst, psittacine bird, avian, umbrella cockatoo, Cacatua alba

CLINICAL REPORT

A 10-year-old female umbrella cockatoo (Cacatua alba), weighing 547 g, presented to the Cummings School of Veterinary Medicine at Tufts University (North Grafton, MA, USA) for assessment of a grape-sized mass, approximately 1 x 2 cm, located at the right commissure of the beak, with associated swelling around the right eye. The owner first noticed the mass approximately 4 weeks before presentation. Previously, the cockatoo had undergone a prolonged molt, and a feather dorsal to the right eye had molted incompletely. The area around the feather base became swollen, so the owner removed the feather with tweezers. The swelling resolved, but within 2 weeks, the mass appeared. Per the owner, the cockatoo was an otherwise healthy bird with no known medical history. It was maintained on a diet composed of 60% safflower seed and 40% pellets, with broccoli, corn, and cauliflower treats (Fig 1).

On physical examination, a round, approximately 1 x 2-cm, firm mass was found at the right commissure of the beak. In addition, right-sided exophthalmos was present, and the scleral ossicles were palpably displaced from within the orbit. Periorbital swelling was suspected to be subcutaneous emphysema. The eye retained normal vision and normal pupil function. The choanal slit appeared subjectively elongated. All other findings on physical examination were unremarkable. Differential diagnoses for the mass included sinusitis, conjunctivitis, neoplasia, squamous metaplasia, and a cyst. To further delineate the mass, computed tomography (CT) was performed.

For the CT study, the patient was premedicated with butorphanol (0.55 mg/kg IM) and midazolam (0.5 mg/kg IM). Anesthesia was induced with sevoflurane gas at 4% provided via face mask. Atropine (0.08 mg/kg IM) was administered during induction to treat bradycardia. The cockatoo was intubated with a 4.5-mm Cole tube, and a 24-gauge catheter was placed in the right medial metatarsal vein. The bird was positioned in sternal recumbency, and the CT was performed with a 16-slice Toshiba Aquilion machine (Canon Medical Systems, Tustin, CA, USA); technique factors included kVp 120, mAs modulated (range 80-120), with 240-mm calibrated field and a 512 x 512 matrix. Data were acquired before and after administration of iodinated contrast material (2 mL/kg IV; iohexol 300 mg/mL; Omnipaque, GE Healthcare, Marlborough, MA, USA). Images were obtained with a slice thickness of 1-2 mm and a detailed pitch. Reconstructions were performed in standard soft tissue (window width [WW] 320, window level [WL] 30), sharp lung (WW 320, WL 30), and high-resolution bone (WW 3200, WL 800) algorithms in dorsal, sagittal, and transverse planes.

Results of the CT imaging showed a soft-tissue attenuating, peripherally contrast-enhancing mass extending from the right infraorbital sinus to the right retrobulbar space, measuring 2.5 x 1.8 cm. Within the ventral portion of the mass, an amorphous, hyperattenuating region was visible. The mass was causing lateral deviation of the right eye but did not appear to be invading the calvarium. The primary differential diagnoses for these findings were a feather cyst, a granuloma, or neoplasia. During the anesthetization of the cockatoo, a fine-needle aspiration of the mass was performed. The patient recovered well from anesthesia (Fig 2).

Analysis of the fine-needle aspirate samples showed rare, nucleated, squamous epithelial cells; small to moderate amounts of nuclear keratinized epithelium; and a viscous or cystic background. No evidence of inflammation, hemorrhage, or neoplasia was found. Cytologic findings supported the diagnosis of a feather cyst, and surgical debridement of the mass was recommended.

Results of a complete blood cell count showed mild to moderate leukocytosis (18.82 x [10.sup.3] cells/ ([micro]L; reference interval, 8.0-16.0 x [10.sup.3] cells/[micro]L), (1) characterized by a mild heterophilia (8.55 x [10.sup.3] cells/jjL; reference interval, 5.79-9.09 x [10.sup.3] cells/ ([micro]L)(1); mild lymphocytosis (7.98 x [10.sup.3] cells/[micro]L; reference interval, 2.56-6.59 x [10.sup.3] cells/[micro]L) (1); and a moderate monocytosis (2.47 x [10.sup.3] cells/[micro]L; reference interval, 0-0.26 x [10.sup.3] cells/[micro]L),' consistent with a chronic inflammatory process or possibly with stress of the previous anesthetic event. All biochemical values were within reference intervals. (1)

Surgery was scheduled 2 weeks after the CT scan. For surgical debridement, the patient was premedicated with butorphanol (1 mg/kg IM) and midazolam (1 mg/kg IM)), and anesthetic induction was performed with 4% sevoflurane administered by face mask. The bird was intubated with a 5-mm Cole endotracheal tube and maintained on sevoflurane gas to effect. A 24-gauge catheter was placed in the right medial metatarsal vein for continuous rate infusion of fentanyl (0.3 mcg/kg per minute) and crystalloid fluids (20 mL/kg per hour).

The patient was placed in left lateral recumbency, and the skin surrounding the right eye was aseptically prepared. A 2.5-cm incision through the skin and periorbital fascia was made starting at the caudolateral aspect of the eye and extending around the rostral-ventral bony orbit just below the lower eyelid, allowing visualization of the most superficial aspect of the cyst. Two stay sutures were placed in the lower eyelid and used to retract the eye slightly dorsal. This allowed visualization of 2 more lobes of the cyst medial to the globe. All exposed lobes were removed with a combination of sharp and blunt dissection. Cotton-tipped applicators were used to remove the caseous contents of the cyst and to aid in debridement of the wall lining (Fig 3). The periorbital fascia of the globe was reapposed with 3-0 poliglecaprone 25 suture (Monocryl, Ethicon, Somerville, NJ, USA) in a simple-interrupted pattern, and the skin was closed with 3-0 Monocryl in a simple-interrupted pattern. The primary perioperative concern was that, given the proximity of the cyst to the eye, the entire contents could not be removed, so recurrence was possible.

The bird recovered uneventfully from anesthesia and was discharged from the hospital the next day. After surgery, the bird received an injection of vitamins A, D, and E (0.27 mL/kg IM; 100 000 U vitamins A/10 000 U vitamin [D.sub.3]/ 300U vitamin E per mL) and a dose of cefazolin (36 mg/kg IM) for antibiotic prophylaxis because of an episode of regurgitation during handling. It was discharged with amoxicillin/clavulanic acid suspension (125 mg/kg PO ql2h for 7 days) and meloxicam (0.5 mg/kg PO ql2h for 2-3 days). (2)

Results of histopathologic examination showed a large cyst lined with keratinizing squamous epithelium and filled with amorphous and lamellar keratin. The wall was composed of a moderately cellular, fibrous capsule, with aggregates of lym phocytes, macrophages, and occasional heterophils, as well as reactive, newly formed capillaries. The adjacent skeletal muscle contained prominent, reactive lymphoid follicles and moderate hemorrhage. The wall of the infraorbital sinus was also included in the biopsy, with no abnormalities observed (Figs 4 and 5). The diagnosis was an infraorbital keratin cyst, likely originating from a feather follicle.

One year after surgery, the owner reported that the cockatoo was doing well and that there was no evidence of recurrence of the mass or the periorbital swelling.

DISCUSSION

Differential diagnoses for periocular masses in birds include an abscess, (3) neoplasia, (4) sinusitis, (5) conjunctivitis, (5) or a cyst. (6-8) In psittacine species, squamous metaplasia with granuloma formation secondary to chronic vitamin A deficiency is also an important differential diagnosis. (3,5,9) To our knowledge, this is the first report of an infraorbital keratin cyst in an umbrella cockatoo, and it adds an important differential diagnosis in cases of periocular masses in avian patients.

Squamous metaplasia is common in psittacine birds that eat a seed-based diet. In these cases, the vitamin A deficiency causes keratin material and necrotic cellular debris to accumulate into plaques on epithelium and mucous membranes. These plaques can progress to granulomas when secondary bacterial or fungal infections occur. This disease process can cause changes to the sinuses and secondary bacterial sinusitis, which could progress to a periorbital swelling, such as seen in this patient. It can also affect the eye directly, causing xerophthalmia and secondary infection, resulting in conjunctivitis and periorbital swelling. (3-5-9)

This cockatoo was fed a diet based 60% on safflower seed. In addition, the periorbital swelling observed could have been caused by abnormalities in the infraorbital sinus or the conjunctiva, both of which are affected by squamous metaplasia. On physical examination, the cockatoo also had an abnormal choanal opening, which can be a location of squamous metaplasia. For these reasons, squamous metaplasia was initially considered the most likely diagnosis, and the patient was treated with vitamins A, and E. However, histopathologic results ruled out squamous metaplasia. The mass, in this case, was composed of keratin, but no necrotic material or infectious agents were identified; both of which are commonly seen in cases of hypovitaminosis A. (5)

A feather cyst is a swelling that forms within the follicle of a growing feather, usually secondary to infection or trauma to that follicle. The feather develops into a cyst, which accumulates keratinaceous material. Keratin cysts commonly develop on the wings at the origin of flight feathers. The cockatoo we describe had a history of a difficult molt and specifically had a feather that the owner removed in the region of the mass. In addition, histopathologic results demonstrated lamellar keratin, consistent with a feather cyst. However, the cyst in this patient formed on the face and also involved the infraorbital sinus, an uncommon presentation for feather cysts, which has not, to our knowledge, been reported previously. (10,11)

A periorbital cyst in a similar location was reported in an umbrella cockatoo (Cacatua alba) that presented with a periorbital swelling. The mass was removed surgically, and histopathologic results determined the mass to be an infraorbital cyst, which formed from the secretory epithelium of the infraorbital sinus. (8) Although the cyst in the cockatoo we describe involved the lining of the infraorbital sinus, it was only partially lined by this secretory epithelium, whereas the cyst in the umbrella cockatoo was completely enclosed within the sinus and lined by its secretory epithelium. In addition, that cyst contained scant eosinophilic secretory material, (8) whereas the cyst in our report was filled with amorphous keratin.

In a recent report, (4) a periorbital mass with extensive lysis of the frontal bone and nasal passages visible on CT was described in an orange-winged Amazon parrot (Amazona amazonica). The bird was euthanized, and the mass was diagnosed as a mucoepidermoid carcinoma in histopathologic examination. (4) Neoplasia was an important differential diagnosis in the cockatoo we describe. However, many aspects of our case were not consistent with neoplasia. In the case report of the Amazon parrot, the mass grew slowly over the course of several months, which is consistent with neoplasia. (4) In the cockatoo of this report, the mass appeared acutely and was static in size and shape. The CT scan in the cockatoo showed no bony destruction, which would be expected in a neoplastic process. (12) In addition, results of the fine-needle aspirate showed no evidence of neoplastic cells. Although these findings did not definitively rule out neoplasia, it was less likely, and histopathologic results ultimately did rule out neoplasia.

For the surgical procedure, doses of premedications were increased in an effort to reduce the amount of sevoflurane needed for induction and to avoid the bradycardia that occurred during the first anesthetic episode. We also used a fentanyl continuous rate infusion to provide analgesia and to reduce the amount of sevoflurane anesthesia needed. The fentanyl dose was extrapolated from canine doses, which are significantly lower than published doses for cockatoos. (13) The rationale behind using this lower dose was that it was used in conjunction with midazolam and butorphanol. In this case, anesthetic induction, maintenance, and recovery went smoothly, and the patient did not seem in need of additional analgesia.

This case demonstrates that a feather cyst is an important differential diagnosis for a swelling associated with a history of abnormal molting in a bird, regardless of the location. Although the prognosis associated with an aggressive neoplastic process would be guarded to poor, removal of this cyst was apparently curative. Additionally, the treatment approaches vary significantly based on an accurate diagnosis. Sinusitis or conjunctivitis would require diagnosis by culture or Gram's stain of infectious organisms and require appropriate antimicrobial or antifungal therapy/ In the case of a feather cyst, the entire contents of the cyst, including the dermal papilla, must be removed to resolve the swelling, and antibiotic therapy alone will not be effective. (10) If the swelling was determined to be squamous metaplasia, diet change and vitamin A supplementation would have been needed, in addition to surgical debridement. (3,10) Sampling of the lesion in this case to determine the underlying cause was important to develop an effective therapeutic approach.

Acknowledgments: We thank Heather Spain. DVM. for her contributions to the CT images and figure legends.

References

(1.) Fudge AM, Speer BL. Normal clinical pathologic data. In: Speer BL, ed. Current Therapy in Avian Medicine and Surgery. St. Louis, MO: Elsevier; 2016:825-855.

(2.) Morrisey JK, Johnston MS. Ferrets. In: Carpenter J, ed. Exotic Animal Formulary. 5th ed. St Louis, MO: Elsevier, 2018:532-557.

(3.) MacWhirter, P. Malnutrition. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian Medicine: Principles and Application. Lake Worth. FL: Wingers Publishing Inc; 1994:842-861.

(4.) Nau M, Carpenter J, Lin D, et al. Mucoepidermoid carcinoma in the skull of an orange-winged Amazon parrot (Amazona amazonica). J Avian Med Surg. 2017;31 (3):225-231.

(5.) Arca-Ruibal. B. Disorders of the respiratory system. In: Samour J. ed. Avian Medicine. 3rd ed. St Louis, MO: Elsevier; 2016:385-395.

(6.) Baine K, Nobrega-Lee M, Jones MP, et al. Branchial cyst with carcinoma in an umbrella cockatoo (Cacatua alba). J Avian Med Surg. 2014; 28(3):232-239.

(7.) Harrison GJ. Microsurgical procedure for feather cyst removal in a citron-crested cockatoo (Cacatua sulphurea citrinocristata). J Avian Med Surg. 2003; 17(2):86-90.

(8.) Stiles J, Greenacre C. Infraorbital cyst in a white cockatoo (Cacatua alba). J Avian Med Surg. 2001; 15(1):40-43.

(9.) Sandmeier P. Disorders of the digestive system. In: Samour J, ed. Avian Medicine. 3rd ed. St Louis, MO: Elsevier; 2016:373-384.

(10.) Forbes N. Soft tissue surgery. In: Samour J, ed. Avian Medicine. 3rd ed. St Louis, MO: Elsevier; 2016:294-311.

(11.) Schmidt RE. Lightfoot TL. Integument. In: Harrison GJ, Schmidt R, Lightfoot T. eds. Clinical Avian Medicine. Vol 1. Palm Beach, FL: Spix Publishing; 2006:395-410.

(12.) Thrall DE. Principles of radiographic interpretation of the appendicular skeleton. In: Thrall DE, ed. Textbook of Veterinary Diagnostic Radiology. 6th ed. St Louis, MO: Elsevier; 2013:252-266.

(13.) Hoppes S, Flammer K. Hoersch K, et al. Disposition and analgesic effects of fentanyl in white cockatoos (Cacatua alba). J Avian Med Surg. 2003; 17(3): 124-130.

Rachel C. Turner, DVM, Jennifer E. Graham, DVM, Dipl ABVP (Avian/Exotic Companion Mammal), Dipl ACZM, Shelley Hahn, DVM, Dipl ACVP, Abigail Mariano, VMD, Dipl ACVS-SA, and Robert McCarthy, DVM, Dipl ACVS

From the Department of Comparative Diagnostics and Population Medicine. College of Veterinary Medicine. University of Florida, 2015 SW 16th Ave, Gainesville. FL 32610. USA (Turner); the Department of Clinical Sciences. Cummings School of Veterinary Medicine at Tufts University, 200 Westboro Rd. North Grafton. MA 01536. USA (Graham. McCarthy); the Department of Pathology. Kimron Veterinary Institute. Bet Dagan. Israel (Hahn): and Boston Veterinary Specialists, 326 Bridge St. Dedham. MA 02026. USA (Mariano).

Caption: Figure 1. Preoperative image of an umbrella cockatoo with mass located at the lateral commissure of the beak, with associated swelling around the right eye.

Caption: Figure 2. Transverse images of the head of the cockatoo described in Figure 1. just caudal to the level of the articulation of the pterygoid and palatine bones, with (a) a standard soft-tissue window precontrast, (b) a standard soft-tissue window postcontrast; and (c) a high-resolution bone window postcontrast. R indicates right. Filling the right infraorbital sinus and extending into the right retrobulbar space, a ~2.5-cm-diameter, minimally heterogeneous, soft tissue-attenuating (pre-HU 30-76), and mildly peripherally contrast-enhancing (post-HU 28-102) mass is present, consistent with keratin cyst (a). There is extension of the mass into the right retrobulbar space with secondary moderate right exophthalmos.

Caption: Figure 3. Intraoperative image of umbrella cockatoo described in Figure 1, with lobes of the mass being retracted by forceps and a cotton-tipped applicator.

Caption: Figure 4. Photomicrograph of the infraorbital feather cyst in the umbrella cockatoo described in Figure 1. Lamellar keratinaceous material is seen along with the normal lining of the infraorbital sinus (arrow) with no histopathologic changes (hematoxylin and eosin, X10, bar = 50 [micro]m). Courtesy of Nicholas Robinson.

Caption: Figure 5. Higher-magnification photomicrograph of the infraorbital cyst described in Figure 4. Lamellar keratinaceous material is seen along with the normal lining of the infraorbital sinus (arrow) with no histopathologic changes (hematoxylin and eosin, X40, bar = 20 urn). Courtesy Nicholas Robinson.
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Title Annotation:Clinical Report
Author:Turner, Rachel C.; Graham, Jennifer E.; Hahn, Shelley; Mariano, Abigail; McCarthy, Robert
Publication:Journal of Avian Medicine and Surgery
Article Type:Clinical report
Date:Jun 1, 2019
Words:2928
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