Nomenclature and Classification of Odontogenic Tumors - Part II: Clarification of Specific Nomenclature

Gingival Mucoperiosteal Fibroma-Clinical, Imaging, and Histological Review of a Novel Oral Fibroma in 27 Dogs

This case series describes the clinical, imaging, and histological features of 27 lesions diagnosed as a benign fibrous mass not previously described in veterinary literature. The authors propose the name gingival mucoperiosteal fibroma (GMPF) to describe these fibrous lesions found in dogs. Histologically, GMPF is characterized by a lack of odontogenic tissue and various degrees of ossification. GMPFs affect adult dogs with an average age of 95 months (range 24-156 months) and appear as expansile growths with superficial appearance matching the surrounding gingiva. The mandibular incisive region is the most commonly affected region (n = 13) and most cases have some level of bone proliferation radiographically (n = 14). Histological examination of the masses shows poorly cellular fibrous tissue with thick interwoven collagen fibers. Bony invasion by the mass was not noted, though histological proliferation of bone was seen in 17 lesions. Surgical resection was curative in all cases when performed, and no recurrence was seen at time of follow-up. Fibrous lesions of the oral cavity in dogs are poorly defined and categorized, though numerous lesions have been described in both human and veterinary literature.

Symphyseal-Sparing Mandibulectomy for Canine Acanthomatous Ameloblastoma in Dogs: 35 Cases

Canine acanthomatous ameloblastoma (CAA) has been reported to be the most prevalent odontogenic tumor in dogs. The most common location of this tumor is the rostral mandible. Symphyseal-sparing mandibulectomy has been shown to be an effective technique to maintain mandibular continuity and promote early return to function. In this retrospective study, 35 dogs with CAA associated with a mandibular canine tooth were evaluated following a symphyseal-sparing rostral mandibulectomy. Dogs with intraoperative transection of the canine tooth root and subsequent root fragment extraction were included. The objective of this study was to evaluate outcome following excision of CAA with mid-root transection. Data retrospectively evaluated in this study included the following: narrowest tumor margin, narrowest tumor margin at the border associated with the transected canine root, tumor size, and prevalence of local recurrence. This study showed that 82.86% of CAA were completely excised with tumor-free margins (N = 29). The median narrowest overall tumor-free margin was 3.5 mm (interquartile range [IQR] 2.0-6.5 mm) and the median tumor-free margin associated with the border of the transected canine root was 5.0 mm (IQR 3.1-7.0 mm). Follow-up data was obtained in 25 cases via phone interviews with referring veterinarians and clients. No local tumor recurrence was reported in cases with incomplete tumor excision (N = 5). All dogs with follow-up data survived at least 1 year following surgery. It was concluded that segmental or rostral mandibulectomy with wide margins to include the entire mandibular canine tooth with subsequent mandibular instability may not be warranted for dogs with CAA associated with this tooth.

Management of hormonal induced recurrent ulcerative fibrous epulis with osseous metaplasia: A case report

Key Clinical Message

Understanding the role of hormones in periodontitis is important. Periodontal microscopic surgery approach in the treatment of fibrous epulis is not indicated. Wider flap access with root planning is indicated to control the lesion in one phase.

Abstract

We present a case of a 40-year-old female who presented with a gingival hyperplastic lesion around the maxillary left permanent central and lateral incisors. Patient's medical history reveals a recent pregnancy, hypothyroidism, ulcerative colitis, and schizoaffective disorder. All medical conditions were controlled by medications. The lesion was excised using a minimally invasive periodontal surgical technique, and the biopsy results confirmed a diagnosis of ulcerative fibrous epulis with osseous metaplasia. No curettage or local debridement was done under the assumption that the patient's oral hygiene was satisfactory and due to aesthetic concerns of gingival recession and creation of black triangles. The lesion recurred after 3 months and was removed using a traditional more invasive surgical technique. The patient was followed up for 2 years, and there was no further recurrence due to the complete excision of the lesion in the second surgery and the disappearance of the hormonal-related factors post-pregnancy that could have contributed to the gingival hyperplasia. The unique component of the case we are presenting is the comparison between two different surgical techniques and the conduction versus absence of local periodontal debridement after surgical excision as well as the possible correlation between oral supplements and the calcific nature of the lesion(s) reported. The case we present demonstrates that a more invasive traditional surgical approach together with local periodontal therapy provide an optimum treatment outcome in conjunction with elimination of any associated etiological factors. We also propose that hormones are more important as an etiological factor in developing fibrous epulis lesions than medical conditions and medications.

Maxillary neoplasms in four dromedary camels

Four camels (Camelus dromedarius) presented to the Veterinary Teaching Hospital at King Faisal University with maxillary masses. On radiographs, the masses were multicystic and expanded the maxillary bone. The tumors were diagnosed by histopathologic examination as conventional ameloblastoma, two cases as intraosseous squamous cell carcinoma, and central odontogenic fibroma with ossification. To the authors' knowledge, this is the first report of ameloblastoma in a camel, the first detailed description of maxillary squamous cell carcinoma in camels, and the first report of central odontogenic fibroma in any animal species.

Clinical, Radiographic and Histologic Evaluation of 40 Cystic Oral Lesions in 37 Cats

Feline cystic oral lesions are uncommon and include odontogenic cysts and cystic odontogenic tumors. Accurate diagnosis requires close collaboration between the clinician's clinical and radiographic findings and the pathologist's histologic interpretations. The odontogenic cysts identified in this series include a periapical cyst, dentigerous cysts and a type of unclassified collateral cyst that appears to be a previously undefined, distinct entity in cats (UCC). Many of the cysts (52%) were unable to be classified due to insufficient diagnostic information, which often related to the associated tooth being unavailable for evaluation. Cystic odontogenic tumors included ameloblastomas, amyloid producing ameloblastomas (APA), and feline inductive odontogenic tumors (FIOT). The purpose of this case series was to assess correlations between clinical and radiographic findings, histopathologic interpretation and signalment to identify common characteristics and provide recommendations for clinicians and pathologists to optimize diagnostic efficiency and accuracy for cystic oral lesions in cats.

Oral Pathology in Portuguese Dogs: An Eight-Year Biopsy-Based Retrospective Study

The oral cavity of the dog can be the site of several types of pathology including both benign and malignant lesions. The aim of this study was to analyze the frequency and clinical-pathological characteristics of oral lesions present in a cohort of Portuguese dogs. A retrospective observational cross-sectional study on 704 canine oral lesions submitted for histopathological diagnosis to a Veterinary Pathology Center in the north of Portugal from 2010 to 2017 was performed. Gender, age, location of the lesion and the histopathological diagnosis was analysed. From the 704 cases included, 307 (43.6%) were females and 397 (56.4%) males. The mean age was 9.53 ± 3.6 years-old (range 3 to 240 months). The site most frequently affected was the gingiva (n = 283; 40.2%). 342 (48.6%) cases were malignant neoplasms, most represented by oral melanoma (n = 129; 37.7%). 256 (36.4%) cases were benign neoplasms, most represented by fibromatous epulis of periodontal ligament origin/peripheral odontogenic fibroma (FEPLO/POF) (n = 208;81.3%). 106 (15%) were non-neoplastic lesions, most represented by gingival hyperplasia (n = 25, 23.6%). This study provides useful information about frequency and distribution of oral lesions in dogs over a period of eight years allowing valuable comparison with other countries and other species. The most common benign tumours were FEPLO/POF while oral melanoma was the most common malignant tumour.

Tumour Incidence in Dogs in Germany: a Retrospective Analysis of 109,616 Histopathological Diagnoses (2014-2019)

Characterization of a tumour entity is based on the precise histopathological diagnosis taking into account the signalment of the diseased animal. The present study is a comprehensive, up-to-date statistical investigation on the type, frequency and breed distribution of neoplasia in dogs in Germany. The histopathological datasets of 109,616 German canine tissue samples (2014-2019) were processed and statistically examined in retrospect. Non-neoplastic diseases were found in 38,650 samples (35.3%) and 70,966 neoplasms (64.7%) were diagnosed. The most common neoplasms were mammary tumours (21.9%), benign epithelial skin tumours (15.4%), mast cell tumour (9.7%), histiocytoma (7.0%), soft tissue sarcoma (5.8%), lipoma (5.8%), melanocytic tumours (5.2%) and odontogenic tumours (4.7%). In general, Beagles, Magyar Vizslas, Boxers, Schnauzers, Spaniels, French Bulldogs and Golden Retrievers had an increased risk of neoplasia (odds ratio 1.17-1.46; all: P ≤0.001) compared with crossbreed dogs. In particular, Boxers, Golden Retrievers, Rottweilers and Schnauzers were often affected by malignant neoplasms, whereas some breeds (eg, West Highland White Terrier, Magyar Vizsla, Chihuahua, Dachshund and Yorkshire Terrier) were frequently affected by numerous benign tumour types. Despite the known risk of haemangiosarcoma in German Shepherd Dogs, other malignant tumours were rare in this breed. Depending on the type of tumour, some purebred dog breeds can have an increased, reduced or identical risk for certain neoplasms compared with crossbreeds. Discussion of breed predispositions to tumour diseases must therefore be conducted critically and with a view to clinical relevance.

Cystic Odontogenic Tumor with Features of Calcifying Odontogenic Cyst in 3 Cats and a Dog

This case series describes the clinical appearance, radiographic appearance and histopathologic features of 4 patients (3 cats and 1 dog) with unique cystic oral lesions that are consistent with a diagnosis of calcifying odontogenic cyst (COC). COC is a rare odontogenic lesion in humans that has not been previously reported in companion animals. Historically, COC in humans has been classified as a benign cystic neoplasm and as a non-neoplastic odontogenic cyst. Current classification favors the latter. The cases in this series also have ambiguous features regarding classification of the lesion as an odontogenic cyst versus benign neoplasia.

Surgical Margins for Ameloblastoma in Dogs: A Review With an Emphasis on the Future

Ameloblastoma is a benign epithelial odontogenic tumor with the capacity to aggressively invade the surrounding bone. Surgical removal of the tumor can result in extended disease-free interval (cure). However, controversy surrounds the most appropriate surgical margin required to prevent local recurrence while simultaneously minimizing morbidity. En bloc excisional surgery carries the risk of major complications such as mandibular drift, hemorrhage, and oronasal fistula formation. Conservative therapy without a safety margin reduces potential morbidity but is likely to result in local recurrence. No reliable rate, nor time to recurrence, is documented but may be as high as 91% with conservative therapy. Conversely, surgery with a 10- to 20-mm margin is associated with a 0–4.6% recurrence rate. There is no documented difference in the recurrence rate with a 10- vs. 20-mm margin. The correlation of the histologic margin with the recurrence rate following excisional surgery has not determined a required histologic safety margin. Rather, no local recurrence occurs despite narrow or incomplete margins. Thus, pathologic margins > 0 mm may be sufficient to prevent local recurrence or recurrence may be protracted. Accordingly, a narrow (5–10 mm) gross surgical margin may be the most appropriate. Additional research is required for confirmation, and only level 4 evidence on safety margins has been achieved thus far. Future work should focus on defining the extension of neoplastic cells past the demarcation of ameloblastoma on variable diagnostic imaging modalities as well as determining the recurrence rate with various surgical and histologic safety margins.

Biological Behavior of Canine Acanthomatous Ameloblastoma Assessed With Computed Tomography and Histopathology: A Comparative Study

Canine acanthomatous ameloblastoma (CAA) appears to have variable biological behavior with some tumors presenting with slow growth and minimal bone loss while others grow rapidly and cause severe cancellous and cortical bone destruction. The primary aim of the study is to elucidate if variations (grades) of CAA can be identified based on both histological and diagnostic imaging indices, and to compare markers of more aggressive behavior between these 2 commonly used diagnostic tools. This study evaluated 45 cases of CAA and confirmed that there is high degree of variability in tumor invasiveness as measured with computed tomography, with predominantly intraosseous tumors being significantly associated with more invasive behavior. However, the analysis also identified that there was very little correlation between computed tomographic and histological appearance of the tumor. CAA tends to have a highly uniform and predictable histological pattern, with tumors that aggressively invade bone (as seen on CT) not showing features of atypia that might be helpful in predicting the biological behavior of the neoplastic cells. Thus, reliance on diagnostic imaging as a measure of biological behavior is recommended for treatment planning as well as possible creation of a variant/grading scheme. Prospective studies are required to evaluate if differing variants of CAA as based on diagnostic imaging should be treated differently, and how this would affect long term clinical outcome.

Oral Lesions in Captive Nondomestic Felids With a Focus on Odontogenic Lesions

Odontogenic lesions are well described in domestic cats, but published literature describing these lesions in nondomestic felids is limited. This study reports oral lesions in 109 captive, non-domestic felids. Ten cases of odontogenic lesions were diagnosed, including 9 with fibromatous epulis of periodontal ligament origin (FEPLO) and one odontogenic cyst in a cougar. FEPLO was common in lions. FEPLO did not recur after surgical removal in any of the 3 cases for which follow-up information was available. Increased occurrences of oral papillomas in snow leopards and eosinophilic granulomas in tigers were identified, which is consistent with the reported literature. With the exception of oral papillomas in snow leopards and FEPLO in lions, the spectrum of oral lesions in nondomestic felids was similar to what is reported in domestic cats, with squamous cell carcinoma being the most common oral malignancy, and stomatitis/gingivitis/glossitis accounting for approximately one third of all cases. Rare diagnoses with one case each included hemangioma, fibrosarcoma, melanoma, cleft palate, and glossal amyloidosis.

Case Report: Amyloid-Producing Odontogenic Tumor With Pulmonary Metastasis in a Spinone Italiano-Proof of Malignant Potential

A 1-year-old male Spinone Italiano dog was treated for an amyloid-producing odontogenic tumor on the right maxilla with a cytoreductive surgery followed by a definitive radiation protocol. Six years later, the dog presented for a new mass on the rostral mandible as well as a lung nodule without recurrence of the original maxillary tumor. Both the mandibular mass and the lung nodule were histologically confirmed to be amyloid-producing odontogenic tumor based on the appearance of sheets and cords of the odontogenic epithelium disrupted by amorphous extracellular amyloid. This case illustrates the metastatic potential for amyloid-producing odontogenic tumor in dogs and asynchronous occurrence of multiple APOTs in the oral cavity.

Presentation, Diagnostic Imaging, and Clinical Outcome of Conventional Ameloblastoma in Dogs

A noninductive tumor of odontogenic epithelium occurs within the tooth bearing regions of the jaw in dogs and fits the conventional definition of ameloblastoma, which is distinct from, and less common than, canine acanthomatous ameloblastoma. In order to clarify the clinical and radiological features of this uncommon odontogenic tumor in dogs, we performed a retrospective study of 20 dogs that were diagnosed between 2007 and 2015. Follow-up information was obtained for 17 of 20 dogs. The study group of dogs showed no apparent age, breed, or gender predilection. Conventional ameloblastoma is typically slow growing, well demarcated, and locally destructive. Tumors most commonly occurred as a mass or focal bony swelling within the maxilla (13/20) or mandible (7/20). Based on cases with available diagnostic imaging, as either dental radiographs or computed tomographic images, the tumors were usually intraosseous and caused mixed lytic/proliferative bone changes. Nevertheless, conventional ameloblastomas did not aggressively infiltrate adjacent tissues and recurrence was not observed within the study group, even in patients with narrow surgical margins or treatment by cyst enucleation.

Diagnosis and Treatment of an Odontogenic Epithelial Tumor in a Dog With Features of Squamous Odontogenic Tumor

A 9-year-old standard poodle presented for a comprehensive oral health assessment and treatment, at which time a left rostral mandibular swelling was recognized. The mass was biopsied and eventually excised by a left rostral mandibulectomy en bloc resection. Histopathology supported the diagnosis of a benign, intraosseous, epithelial tumor that was otherwise unclassified. The clinical, radiological, and histological features of this case are similar to those reported for squamous odontogenic tumor (SOT) in humans. This case study relays the diagnosis, treatment, and follow-up of the first SOT-like tumor in a dog.

Ki67 Labelling Index of Neoplastic Epithelial Cells Differentiates Canine Acanthomatous Ameloblastoma from Oral Squamous Cell Carcinoma

Canine acanthomatous ameloblastoma (CAA) and oral squamous cell carcinoma (OSCC) are the most common oral tumours of epithelial origin in dogs. Overlapping clinical, radiographical and histological features can make distinction between CAA and OSCC difficult. The ability to distinguish tumour identity is critical due to their different biological behaviour and recommended treatment modalities, as well as respective comparative and translational applications as potential models of human disease. Based on marked differences in biological behaviour (i.e. benign versus malignant), it is reasonable to predict that the tumour cell proliferation activity is lower in CAA than in OSCC. However, to our knowledge, the epithelial cell proliferation activity of CAA has not been studied or compared with that of OSCC. Therefore, the aims of this study were to (1) compare the neoplastic epithelial cell proliferation activity of CAA and OSCC based on conventional mitotic index (MI) and Ki67 labelling index (LI), and (2) correlate these findings with clinical parameters including patient signalment, anatomical tumour location and degree of local invasion at the time of diagnosis as determined by computed tomography. We found that (1) the Ki67 LI of OSSC (n = 14) was significantly higher than that of CAA (n = 25), (2) the Ki67 LI correlated with a more aggressive locally invasive behaviour, and (3) the MI was not associated with tumour type. We conclude that the Ki67 LI, but not the MI, is a useful differential marker of CAA from OSCC, and that the epithelial cell proliferation activities of OSCC and CAA correlate with their known differences in biological behaviour.

Maxillary and Mandibular Peripheral Odontogenic Fibromas (Fibromatous Epulides of Periodontal Ligament Origin) in a Cat

Peripheral odontogenic fibroma (POF) is an uncommon finding in the mouth of cats. Few cases have been reported in the literature. The present report describes an adolescent, male-castrated domestic shorthair cat with POFs at the rostral upper and lower jaws that were treated via marginal excision including removal of underlying bone. Despite the high incidence of recurrence reported in the literature, recheck examinations up to 11 months postoperatively did not show regrowth of the gingival masses. Thus, marginal excision including removal of underlying bone appears to be a viable treatment option for POF in cats.

Mixed odontogenic tumors in four young dogs: ameloblastic fibroma and ameloblastic fibro-odontoma

Ameloblastic fibroma (AF) and ameloblastic fibro-odontoma (AFO) are mixed odontogenic tumors (odontogenic tumors with induction) that are reported only rarely in dogs. These tumors are histologically complex and, to a degree, recapitulate the early stages of tooth development, comprising 2 types of tissue: neoplastic odontogenic epithelium, and induced ectomesenchyme (dental pulp). AFOs are distinguished from AFs by the additional presence of hard dental matrices such as dentin. Herein, we describe the key diagnostic features of AF and AFO in 4 young dogs.

Extensive Maxillary Odontomas in 2 Dogs

Two immature male dogs were presented for the treatment of extensive maxillary compound odontomas. In both cases, clinical evaluation and diagnostic imaging revealed extensive lesions invading and displacing anatomical structures of the maxilla. Histopathology confirmed the diagnoses in both cases. One dog was treated with partial rostral maxillectomy, and the other dog was treated with enucleation of the cystic lining and removal of tooth-like structures through a lateral rhinotomy utilizing an intraoral approach. This report illustrates the growth potential of maxillary compound odontomas in 2 dogs and highlights their subclinical appearance and excellent prognosis despite their extensive nature.

Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig

Odontoameloblastomas (previously incorporated within ameloblastic odontomas) are matrix-producing odontogenic mixed tumors and are closely related in histologic appearance to the 2 other types of matrix-producing odontogenic mixed tumors: odontomas and ameloblastic fibro-odontomas. The presence or absence of intralesional, induced non-neoplastic tissue must be accounted for in the diagnosis. Herein we describe a naturally occurring odontoameloblastoma with extensive chondroid cementum deposition in a guinea pig ( Cavia porcellus). Microscopically, the mass featured palisading neoplastic odontogenic epithelium closely apposed to ribbons and rings of a pink dental matrix (dentinoid), alongside extensive sheets and aggregates of chondroid cementum. The final diagnosis was an odontoameloblastoma given the abundance of odontogenic epithelium in association with dentinoid but a paucity of pulp ectomesenchyme. Chondroid cementum is an expected anatomical feature of cavies, and its presence within the odontoameloblastoma was interpreted as a response of the ectomesenchyme of the dental follicle to the described neoplasm. Our case illustrates the inductive capabilities of odontoameloblastomas while highlighting species-specific anatomy that has resulted in a histologic appearance unique to cavies and provides imaging and histologic data to aid diagnosis of these challenging lesions.

Clinical Characterization of Canine Acanthomatous Ameloblastoma (CAA) in 263 dogs and the Influence of Postsurgical Histopathological Margin on Local Recurrence

Canine acanthomatous ameloblastoma (CAA) has been reported to be the most common odontogenic tumor in dogs. This retrospective study evaluated 263 dogs with histopathologically confirmed CAA. Within this data set, CAA presents most commonly in the rostral mandible in adult large breed dogs, with golden retriever dogs being overrepresented. Patients with appropriate follow-up after curative intent surgery were evaluated to assess the effect of histopathological margin on local tumor recurrence. No local recurrence was noted in any patient. This study raises questions about what the recommended surgical margin should be for treatment of CAA. It also serves as a stimulus for discussion as to whether further treatment for CAA is required when inadequate surgical margins are obtained, or if medical surveillance would be an appropriate management recommendation. Prospective studies are necessary to answer these questions.

Suspected Lateral Periodontal Cyst Presenting Concurrently with Canine Acanthomatous Ameloblastoma in a 2-Year-Old Standard Poodle

Lateral periodontal cysts (LPCs) are odontogenic epithelial cysts composed of nonkeratinized epithelial cells that are in the category of developmental cysts, rather than inflammatory cysts. Lateral periodontal cysts are rare both in people and domestic animals; they are associated with vital teeth and located lateral to a tooth root. Lateral periodontal cysts are typically asymptomatic lesions that are characterized radiographically as a unilocular lucency with well-defined corticated borders. Canine acanthomatous ameloblastoma (CAA) is the most common odontogenic neoplasm in dogs and rarely presents as a cystic lesion. This case report describes the diagnosis and treatment of a cyst that occurred as a swelling apical to a gingival mass that was diagnosed histologically as CAA. Surgical management by conservative gingivectomy, cyst enucleation, and bone grafting was an effective treatment in this patient.