pISSN 1598-298X
J Vet Clin 31(2) :159-162 (2014)
159
Ossifying Epulis in a Thoroughbred Foal
Joon-Gyu Kim*†, Seong-Hwan Mun**†, Kyu-Ryeon Ko and Jae-Hoon Kim1
College of Veterinary Medicine and Veterinary Medical Research Institute, Jeju National University, Jeju 690-756, Korea
*Jeju Studfarm, Korea Racing Authority, Jeju 695-811, Korea
**Jeju Self-Governing Provincial Veterinary Research Institute, Jeju 695-963, Korea (Accepted: February 15, 2014)
Abstract : A 4-month-old female thoroughbred foal was presented with large mass on mandibular gingiva. The enlarged mass was firm and yellowish pink in color, and occupied the whole mandibular arcade. The filly could not close her mouth with her lips. Radiographs showed radioopaque mass under the mandible. The mass was surgically excised from mandible. Histopathologically, gingival mass was characterized by hyperplastic gingival epithelium, well vascularized collagenous stroma and large area of bony tissues. Based on the gross and histopathologic findings, this case was diagnosed as ossifying epulis in the mandibular gingiva. This is the first report of ossifying epulis in a thoroughbred horse in Korea.
Key words : foal, gingiva, ossifying epulis, surgery, thoroughbred.
Introduction
Epulis is a benign local exophytic growth of the oral mucosa, derived from the periodontal ligament or connective tissue, occur commonly in dogs and rare in other domestic animals (1,7,8). According to histological characteristics, four types of epulides can be classified in dogs; fibromatous, acanthoma- tous, ossifying and giant cell epulis (1,10). Fibrous epulis (gingival hyperplasia, fibrous hyperplasia) is regarded as a progressive, non-neoplastic benign condition that results in fibrous enlargement of the gingiva along the maxillary and mandibular dental arcades (4,9). Gingival hyperplasia and tumors are common in dogs, but extremely rare in other ani- mals (9). There are three reports of fibrous epulis in horses, that, indicating it is rare in this species (4,5,9). In this report, we described a case of fibromatous epulis (ossifying type) in a filly and the surgical treatment for this lesion.
Case
A 4-month-old female thoroughbred foal was referred to the Equine Hospital of Korea Racing Authority Jeju Studfarm for a gingival mass on mandible. The enlarged mass was firm and yellowish pink in color, and occupied the whole mandibu- lar arcade (Fig 1A). The size was approximately 10 cm in length and 3 cm in depth. The foal had been treated with antibiotics and NSAID for one week by a local veterinarian.
The filly’s general condition was good and 180 kg in body
weight.
The filly could not close her mouth with her lips because of the mass. The rectal temperature, complete blood cell count and biochemical profiles were within normal range. Radio- graphs showed radioopaque mass under the mandible (Fig 2).
Prophylactic antimicrobials including penicillin G procaine (20,000 IU/kg, IM, PPS®, Daesung Microbiological Labs.
Co. Ltd.) and gentamicin (6.6 mg/kg, IV, GENTAMYCIN®, Daesung Microbiological Labs. Co. Ltd.) as well as flunixine meglumine (1.1 mg/kg, IV, FINADYNE®, Schering-Plough) were administered 1h before induction of general anesthesia.
The patient was premedicated with detomidine hydrochlo- ride (0.02 mg/kg, IV, DOMOSEDAN®, Pfizer Korea Inc.).
Anesthetic induction was accomplished with Diazepam (0.22 mg/kg, IV, DIAZEPAM®, Samjin Pharm Co. Ltd.) and Ket-
†These authors contribute equally to this work
1Corresponding author.
E-mail: kimjhoon@jejunu.ac.kr
Fig 1. Mouth of foal. Proliferated gingival mass occupied in the whole mandibular arcade so the filly could not close her mouth with her lips (A). Note healed mandibular gingiva 14 days after surgery and the filly could close her mouth completely (B).
160 Joon-Gyu Kim, Seong-Hwan Mun, Kyu-Ryeon Ko and Jae-Hoon Kim
amine (2 mg/kg, IV, KETAMINE®, Huons. co. Ltd.). Anesthe- sia was maintained by inhalation with isoflurane.
The patient was placed in dorsal recumbency. Incision was made around gingival mass. The whole mass was removed from the lesion and submitted for histopathological examina- tion. After debridement with curetting, gingiva was closed using tension sutures. After surgery, the foal received antibi- otics and NSAID for 2 weeks. The surgical site was irrigated with diluted chlorhexidine (0.05%) and applied antimicro- bial ointment (tobramycin) every day.
The radiographs taken 14 days post-surgery (DPS) did not show any complications with the repair (Fig 1B). The stitches were removed. The status of healing was good.
After surgery, excised gingival mass was fixed in 10%
buffered formalin, and submitted to the pathology laboratory at the College of Veterinary Medicine in Jeju National Uni- versity. Submitted mass were trimmed, embedded in paraf- fin, sectioned at 3µm, and stained with hematoxylin and eosin (H&E) for light microscopic examination. Special staining such as Masson’s trichrome (MT) and von Kossa staining also performed on paraffin embedded tissue sections.
Histopathologically, neoplastic gingival mass was typically divided into three structures; proliferated gingival epithelium, hyperplastic gingival stroma and embedded bony tissue. Gin- gival epithelium showed severe diffuse hyperplasia and par- akeratosis with moderate rete ridge down growth (Fig 3A).
Most prickle cells had typical intercellular bridge and showed moderate ballooning degeneration and spongiosis. Severe mul- tifocal ulcerations with many bacterial colonies were observed in covered epithelium. Therefore acute inflammation was pre- sented beneath the area of epidermal ulceration. Gingival stroma was hyperplastic with interwoven bundles of stellate to spindle-shaped immature fibroblastic tissues (loose or dense connective tissues) and scattered vascular structure (some new formed vessels, or empty vessels). These immature fibroblasts produced dense fibrillar collagens stained blue with MT stain- ing (Fig 3B). Approximately 60~70% of gingival stroma in the central area of requested sample were replaced by imma- Fig 2. Radiographs showed radioopaque mass (arrow) under the
mandible.
Fig 3. Histopathologic findings of ossifying epulis in a foal. Note hyperplastic squamous epithelium and prominent rete ridges. H&E,
× 100 (A). Stellate and spindle fibroblasts in gingival stroma produced blue stained collagen background. MT, × 100 (B). Numerous immature bony tissues were embedded in stroma. H&E, × 100 (C). Bony matrices were stained black. Von Kossa, × 100 (D).
Ossifying Epulis in a Thoroughbred Foal 161
ture bony tissues composed of osteoid and cementum-like materials (Fig 3C). These bony matrices were stained black with von Kossa staining (Fig 3D).
Discussion
Epulis is considered as the generic and clinical term for tumor-like masses on the gingiva and has been used to describe developmental, inflammatory, hyperplastic and neoplastic lesions (6,7). Because it has no specific pathologic connota- tion, the term should not be used in a morphologic diagnosis, except in the context of fibromatous epulis of periodontal lig- ament origin (6). Fibromatous epulis of periodontal ligament origin is microscopically characterized by a dense, well vas- cularized stroma produced by stellate cells with abundant fibrillar collagen resembling the periodontal ligament (1). It is regarded as a peripheral odontogenic neoplasm, indistin- guishable clinically from fibrous hyperplasia (6). When the bone-like matrix becomes a major component, the epulis is called an ossifying epulis.
The stromal component of fibrous hyperplasia consists of mature fibrous tissue with low cellular density without bone matrix (6,9). On the contrary fibrous hyperplasia, fibromatous epulis is comprised of small stellate to fusiform fibroblasts with dense collagen matrix, less inflammatory elements, and more hard tissues (6). Based on the clinical, histopathologi- cal and gross findings, this case was diagnosed as ossifying epulis in the mandibular gingiva of the horse. Histopatho- logic features of this case were in agreement with most char- acteristics reported for canine and feline ossifying epulis (1,10).
Gingival hyperplasia in horse is often associated with chronic inflammation, malocclusion, or periodontal disease, as seen in some breeds of dogs (4,9). According to previous clini- copathological study of canine oral epulides, the fibromatous and ossifying epulides occurred in close association with chronic gingivitis due to dental plaque deposition or chronic irritation (10). It was postulated that long-term metaplastic bone production in fibromatous epulis may eventually reach the extent of an ossifying epulis (8). Therefore chronic irrita- tion might be closely associated with the occurrence of ossi- fying epulis in this case.
Based on the previous literatures, gingival hyperplasia was reported in old horses, over 18 years old (4,9). And one case of fibromatous epulis was demonstrated on the gingiva of the right mandible of 16 years old mixed breed stallion (3). In addition, as observed in the present case, ossifying epulis may also occur in very young foal.
Because fibromatous or ossifying epulis are all benign tumors, they are cured after surgical excision. After surgical removal, there were no recurrences of gingival hyperplasia in horses (4,9), the same as in this case. But the acanthomatous epulis show high, rapid recurrence and has a poor prognosis.
Hemimandibolectomy and bleomycin chemotherapy were thought to be effective for the acanthomatous epulis (10).
According to the survey of dogs, the average age of the acanthomatous epulis (7.8 years) was slightly lower than that of the fibromatous (8.8), ossifying (8.4) or giant cell epulis (8.7) (10). About 18% (6/34) of dogs with acanthomatous epulis were aged 1-3 years. In addition, 50% (6/12) of cats with fibromatous and/or ossifying epulis were reported 3 years old or younger, suggesting a higher prevalence in young cats (2). This report also suggested that fibromatous or ossifying epulis should be considered as a differential diag- nosis for gingival mass of foal and adult horses.
There was no report describing ossifying epulis in thor- oughbred horses. In this study, we described the first case of ossifying epulis in a very young thoroughbred foal and the successful surgical treatment in Korea.
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162 Joon-Gyu Kim, Seong-Hwan Mun, Kyu-Ryeon Ko and Jae-Hoon Kim
더러브렛 망아지에서 발생한 골화성 치은종
김준규*·문성환**·고규련·김재훈1
제주대학교 수의과대학, 수의과학연구소, *한국마사회 제주육성목장, **제주특별자치도 동물위생시험소
요 약 : 4개월령 더러브렛 암컷 망아지가 하악 치은의 큰 종괴로 인해 내원하였다. 증식된 종괴는 단단하고 황색 기 미의 분홍색을 띠고, 하악 잇몸 전체에 분포하고 있었다. 암망아지는 종괴로 인해 입술을 다물 수 없었고, 방사선상 아 래턱의 종괴 음영이 확인되었다. 종괴는 전신마취상태에서 외과적으로 제거되었다. 병리조직학적으로 잇몸 종괴는 증 식된 잇몸 상피, 혈관이 발달한 교원성 기질 및 많은 골조직으로 구성되어 있었다. 이와 같은 육안 및 병리조작학적 특징을 토대로 하악 잇몸에서 발생한 골화성 치은종으로 확진되었다. 본 증례는 한국에서 더러브렛 망아지에서 발생 한 골화성 치은종의 첫 보고이다.
주요어 : 망아지, 치은, 골화성 치은종, 수술, 더러브렛
