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

Maxillary Ameloblastoma in an Asiatic Black Bear (Ursus thibetanus)

An approximately 30-year-old intact female Asiatic black bear (Ursus thibetanus) was presented for annual examination and a history of ptyalism. A large 9.5 cm × 5 cm × 5 cm, firm, round mass was identified attached to the hard palate on physical examination. A computed tomography scan was performed, and the heterogeneous, mineral-attenuating mass was seen arising from the right aspect of the palatine bone and extending rostrally to the level of the last maxillary molars, caudally into the oropharynx, and dorsally into the nasal choana. Surgical debulking was performed to remove the portion of the mass within the oral cavity. Histopathologic analysis was consistent with a keratinizing ameloblastoma. Nine months postoperatively, the patient was asymptomatic for the tumor. The patient was euthanized 23-months postoperatively, and severe diffuse pustular dermatitis, growth of the ameloblastoma on the hard palate, and various degenerative and aging changes were noted on necropsy at that time. This is the first report of an ameloblastoma in a member of the Ursidae family.

Desmoplastic histological subtype of ameloblastoma in 16 dogs

Ameloblastoma in dogs most often has a highly conserved acanthomatous cell morphology and is recognized as canine acanthomatous ameloblastoma (CAA) while conventional ameloblastoma (CA) makes up a smaller yet morphologically diverse group of epithelial odontogenic tumors. In humans, a rare desmoplastic histological subtype has distinctive clinical, radiological, and microscopic features. Desmoplastic ameloblastoma (DA) has not previously been described in dogs, although it has been rarely referenced in the veterinary literature. This is the first thorough description of a case series of DA in dogs and describes clinical presentation, diagnostic imaging findings, histopathological features for diagnosis, and treatment outcome. Clinically, DA most often presents as a mass or swelling in the rostral mandible or maxilla of middle age to older dogs. On diagnostic imaging, the lesion has a radiolucent or mixed pattern with well-defined borders and variable loculation. As a solid, fibrous tumor with obscured odontogenic epithelium, DA is challenging to diagnose histologically and can mimic several other oral tumors, both benign and malignant. As an ameloblastoma, the biological behavior of DA is locally destructive yet benign and prognosis is favorable following surgical excision.

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.

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.

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.