37 Uludag Univ. J. Fac. Vet. Med. 36 (2017), 1,2: 37-39 Mandibular Osteoma in a Brown Bear (Ursus arctos) Geliş Tarihi:22.06.2017 Düzeltme Tarihi: 10.07.2017, Kabul Tarihi:15.12.2017 M. Ozgur OZYIGIT1*, Huseyin CIHAN2, Nilufer AYTUG 3 Abstract: A 21-year old, 150-kg male Brown bear, kept in Karacabey Bear Sanctuary in Bursa, Turkey, (Ursus Arctos) with an osteoma of the left mandible is presented. A large mass, causing significant facial asymmetry, on the mandible was detected. On palpation, the mandibular mass was very firm and immobile. Macroscopically the mass was non-hyperemic, spherical and smoothly contoured, whitish colored, hard and was 9 cm in diameter and covered by gingival mucosa. Microscopically, the tumoral mass on the mandible was covered with a layer of keratinized squamous epithelium. In deeper layers, bony islands of various shape and size were encountered. Some of them were compact, while some of them were trabecular. No mitotic figures were observed. The clinical and pathological findings were found compatible with osteoma. Key Words: Brown bear, mandible, osteoma, pathology, Ursus arctos. Kahverengi Ayıda Mandibular Osteoma Olgusu Özet: Bu çalışmada, Bursa'nın Karacabey Ayı Koruma Barınağında bulunan 21 yaşındaki 150 kg ağırlığında erkek bir kahverengi ayıda (Ursus Arctos), sol mandibulada bulunan osteoma tümörü tanımlanmıştır. Mandibu- lada belirgin yüz asimetrisine neden olan kitle palpasyonda, sert ve hareketsizdi. Makroskopik olarak kitle hiperemik olmayan, küresel ve düzgün şekilli, beyazımsı renkli, sert ve 9 cm çapındaydı ve diş eti mukozası ile örtülmüştü. Mikroskobik olarak, mandibuladaki tümöral kitle, keratinize skuamöz epitel tabakası ile kaplıydı. Epitel tabakasının altında, çeşitli şekil ve büyüklükteki kemik doku adalarına rastlandı. Kemik dokunun kompakt ve trabeküler yapıdan oluştuğu görüldü. Alanda herhangi mitotik figürlere rastlanmadı. Yapılan klinik ve patolojik bulgular osteomayla uyumlu bulundu. Anahtar Kelimeler: Kahverengi ayı, mandibula, osteoma, patoloji, Ursus arctos. Introduction also seen in wild animals.1,4 Osteomas are slow- ly growing lesions that are normally asympto- Osteoma is a benign bony outgrowth of matic .6 They only present if their location with- membranous bones. These tumors are uncom- in the head and neck region cause problems mon and are found mostly on mandible, maxil- with disfigurement, breathing, prehension and la, nasal sinuses and cranium, and seldom in mastication, deglutition of food, vision and domestic animals, with a more common occur- hearing.5,6,9 In this report, we describe a case of rence in horses and cattle.2,5,6,9,10 the tumor is mandibular osteoma presenting with the com- plaint of facial asymmetry in a brown bear. 1 Uludag University, Faculty of Veterinary Medicine, Department of Pathology, Gorukle Campus, 16059, Bursa, Turkey. *ozyigit@uludag.edu.tr 2 Uludag University, Faculty of Veterinary Medicine, Department of Internal Medicine, Gorukle Campus, 16059, Bursa, Turkey. 3 Near East University, Faculty of Veterinary Medicine, Department of Internal Medicine, Lefkoşa/KKTC, Mersin 10- Turkey. 38 Material and Methods compact, while others were trabecular (Figure 2). The trabecular bones were seen peripherally, Physical examination was performed af- while the compact bones were centrally located. ter chemical restrain using xylazine (Rompun® The compact and trabecular bones were formed Dry Substance, Bayer, 2 mg/kg bw) + Ketamine by mineralized woven bone, with a basophilic HCL (Alfazine® 10%; 100mg/L, Alfasan, Tur- matrix composed of randomly organized fibers, key, 4 mg/kg bw), combination. For extraorally and bordered by a layer of connective tissue approaching and excision of the tumoral mass resembling the osteoblasts (Figure 3). The com- on the mandible, general anesthesia with pact bones had no Havarsian canals and bone xylazine (Rompun® Dry Substance, Bayer, 2 marrow, while the trabecular bones had. The mg/kg bw) + Ketamine HCL (Alfazine® 10%; appearance of stroma was uniform throughout 100mg/L, Alfasan, Turkey, 4 mg/kg bw) com- the sample and there was vascularized light bination, was performed. As there was no func- connective tissue, including collagen fibers and tional impairment of the left temporo- fibroblasts between the trabecular and compact mandibular joint, no operative correction was bone. No mitotic figures were observed. performed of the enlarged condyle. Findings A 21-year old, 150-kg male Brown bear (Ursus arctos), kept in Karacabey Bear Sanctu- ary in Bursa, Turkey, was presented with a pain- less swelling of the left mandible (Figure 1). Keepers had noticed the swelling two weeks prior to the referral of the animal. The animal had good appetite, but had a significant facial asymmetry. A large mass was detected on the mandible. On palpation, the mandibular mass was very firm and immobile. Radiological ex- Figure 1. The tumour (T), located in the left- amination could not be performed. Haematolog- mandible (arrow), was very firm and im- ical and serum biochemical parameters were mobile within normal ranges. Because of the facial asymmetry and the progression of the lesion, Şekil 1. Sol çenede (ok) oldukça sert ve ha- decision was made for operative correction. reketsiz tümör (T) After operation, the mass was kept for histo- pathological examination. The tumor was cut with electric saw and tissue samples were fixed in 10% neutral, buffered formalin and then were decalcified by immersing the mass in 25% for- mic acid and formaldehyde mixture for 3 weeks. Then the tissues were routinely processed and embedded in paraffin. Paraffin embedded tumor samples were cut at 5 µm and stained with hae- matoxylin and eosin (H&E). Macroscopically the mass was whitish colored, spherical and smoothly contoured, 9 cm in diameter and cov- ered with gingival mucosa. On the cut surface of the mass, sectioned with a saw, dense trabec- ular bone was found. Microscopically, the tu- moral mass was covered with a layer of keratin- ized squamous epithelium of the gingiva. The Figure 2. Compact bone of various shape and mass was located under normal gingival epithe- size (arrows), Bar= 90µ, H&E lium. Under the gingival stroma, there was lam- Şekil 2. Farklı şekil ve büyüklüklerde kompakt ina propria, composed of dense collagen fibers. kemik dokusu (oklar) Bar= 90µ, H&E In deeper layers, bony islands of various shape and size were encountered. Some of them were 39 findings about the regrowth of osteomas follow- ing removal.8,9 In the present case, the bear is still under observation and no recurrence has been observed during the 24 months after sur- gery. Acknowledgments This case report was presented at 6thEuropean Association of Zoo and Wildlife Veterinarians (EAZWV), Budapest, Hungary, 2006 Figure 3. Light connective tissue (arrows) re- References sembling osteoblasts surround the compact bone, Bar=22 µ, H&E 1. Hahn, K.A., M.P. Jones, Petersen, M., PattersonM.M., 1998. Clinical and pathological characteri- Şekil 3. 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