Orofacial masses in domestic rabbits: a retrospective review of 120 cases from 2 institutions, 2000-2023

Orofacial masses or swellings are a common presenting complaint in lagomorphs. Similar gross appearances of the masses can complicate clinical interpretation, and histologic review often provides the final diagnosis. Underlying causes vary from infectious to neoplastic. Although inflammatory changes are most commonly reported, various neoplasms occur, although the prevalence of specific tumor types is relatively unknown. We reviewed retrospectively 120 cases (87.5% biopsy, 12.5% autopsy) of neoplastic and non-neoplastic orofacial masses received from January 2000-February 2023 at 2 institutions: University of Guelph, Canada (Animal Health Laboratory and Department of Pathobiology), and Finn Pathologists, United Kingdom. All final diagnoses were achieved through histologic assessment. We included masses or mass-like swellings from the oral cavity, including the mandible and maxilla, and surrounding skin and soft tissues of the oral cavity and jaw. Submissions included pet and commercial (meat and fur) rabbits. Neoplastic lesions were most common (60%), including trichoblastomas, papillomas, melanocytic neoplasms, sarcomas, round-cell tumors, carcinomas (including squamous cell carcinoma), lipomas, odontogenic neoplasms, polyps, osteoma, neuroma, peripheral keratinizing ameloblastoma, and apocrine adenoma. Inflammatory diagnoses (30%) included abscesses, osteomyelitis, dermatitis, and sialadenitis. Other diagnoses (7%) included cysts, as well as hyperplastic skin and proliferative bone lesions. Three cases had no definitive diagnosis. The importance of histologic assessment in diagnosing orofacial "masses" in rabbits is highlighted, given that the most common diagnostic category overall was neoplasia.

Ameloblastic Fibro-Odontoma

Introduction: Ameloblastic fibro-odontoma (AFO) is a benign odontogentic tumor without an aggressive behavior, unlike the similar ameloblastic fibroma. Case Presentation: A 9-year-old boy, with tooth eruption failure, underwent enucleation and curettage of a well-defined variable radiolucent and radio-opaque right mandible lesion. There was odontogenic epithelium with peripheral palisading in a loose myxoid stroma as well as a disorganized component of dentin, enamel, and cementum, features of an AFO. Conclusion: AFO is an odontogenic mixed tumor of epithelium and mesenchyme.

A combination of follicular and plexiform ameloblastoma: A rare case report

Ameloblastoma is a benign but locally aggressive neoplasm of odontogenic epithelium origin. Follicular type is the most common variant of ameloblastoma followed by plexiform, acanthomatous, and granular subtypes. Synchronized existence of plexiform ameloblastoma with follicular ameloblastoma is a rare event. When the plexiform type coexists with other common variant, it is termed as hybrid ameloblastoma. Here, we present a case of hybrid ameloblastoma with follicular and plexiform variants occurring in a 43-year-old female patient having persistent swelling for 5-6 months in the left mandibular body region extending up to the left angle of the mandible. The tumor was treated by en bloc resection followed by reconstruction.

Ameloblastic carcinoma in horses: case report and literature review

Ameloblastic carcinoma is a malignant odontogenic neoplasm that has been reported only rarely in veterinary species. A 16-y-old Arabian crossbred mare was presented for evaluation of a hard mass on the body of the mandible, with evidence of osteolysis on radiographs. Incisional biopsies revealed an invasive neoplasm comprised of spindloid epithelial cells with a high mitotic count and partial dual cytokeratin-vimentin immunoreactivity. The horse was euthanized because of rapid tumor progression 3 mo after presentation. Postmortem evaluation revealed partial obliteration of the mandible by a large, firm-to-hard, tan, locally destructive and invasive mass with no gross or histologic evidence of metastasis. Postmortem histology revealed a poorly differentiated epithelial neoplasm with variably prominent features suggestive of odontogenic histogenesis: a plexiform ribbon architecture, infrequent basilar palisading with antibasilar nuclei, rare basilar cytoplasmic clearing, subepithelial matrix hyalinization, and partial dual cytokeratin-vimentin immunoreactivity. Features of malignancy included regions of necrosis, pronounced cellular atypia, a high mitotic count, extensive tissue invasion and local tissue destruction, and extension of neoplastic cells beyond the margins of the mandibular bone. Collectively, these features are most consistent with mandibular ameloblastic carcinoma. Including our case described here, ameloblastic carcinoma has been reported in only 5 horses. The microscopic features reported most consistently are dual cytokeratin-vimentin immunoreactivity, a high mitotic count, and basilar palisading. Ameloblastic carcinoma should be considered as a differential diagnosis for rapidly growing, locally invasive masses arising from the dentate jaw of horses.

Dentinogenic ghost cell tumor: Case report of a rare central variant and literature review

The dentinogenic ghost cell tumor (DGCT), a solid variant of the calcifying odontogenic cysts, is an uncommon odontogenic neoplasm which is aggressive and has a propensity for recurrence. It accounts for <0.5% of all odontogenic tumors which can exhibit intraosseous (central) or extraosseous (peripheral) localization. Till today, only 39 cases of central DGCT have been reported in English literature according to WHO 2017 Classification. Therapeutic intervention of central variant should be aggressive, local resection with adequate safety margins and monitoring the patient for recurrence as the lesions show recurrence rate up to 71%. The purpose of this paper is to describe a rare case report of central DGCT in a 57-year-old female patient with a brief review of literature which provides an update on the epidemiology, diagnostic and clinicopathological characteristics of the published cases.

Benign cementoblastoma involving left deciduous first molar: A case report and review of literature

Cementoblastoma, a benign mesenchymal odontogenic neoplasm is derived from ectomesenchymal cells of the periodontium. Cementoblastomas associated with primary teeth are extremely rare as permanent mandibular first molars are mostly affected. Only 17 cases of those associated with deciduous dentition have been reported so far. The present case report describes a true cementoblastoma of an 8-year-old male child in relation to the left first primary mandibular molar along with emphasis on differential diagnosis.

Recurrent ameloblastoma of the mandible with unusual granular cell component

Ameloblastomas can present in various clinical and histomorphologic patterns. The granular cell variant accounts for only 3.5% to 5% of ameloblastomas. The aim of this case report is to present an example of ameloblastoma with unusual granular cell component, affecting a 63-year-old woman, in which both the inner and peripheral layers of follicles composed exclusively by eosinophilic granular cells. Assessment of the immunohistochemical and histochemical profile of the lesion was performed and the challenges of such a diagnosis were also addressed.

Central granular cell odontogenic tumor: a systematic review

Central granular cell odontogenic tumor (CGCOT) is a rare benign odontogenic neoplasm reported with various terms and is not included in the 2005 WHO classification of odontogenic tumors. It shows a predilection for middle-aged women, usually presenting as an asymptomatic swelling of the mandibular premolar-molar region. Radiographic manifestations include unilocular or multilocular radiolucent lesion, but mixed density lesions can also occur. Histopathology shows sheets and lobules of round to polygonal cells with abundant eosinophilic, granular cytoplasm and eccentrically placed nuclei. Immunohistochemical and ultrastructural features suggest the histiocytic origin of granular cells. The neoplasm does not exhibit an aggressive biological behavior and hence enucleation or curettage ensuring complete removal remains the treatment of choice. We present a systematic review on clinical, radiological, histopathological, immunohistochemical and treatment aspect of CGCOT. Published articles were identified through a literature search using online databases (PubMed, MEDLINE, Scopus) and cross-references for papers published from the year 1950 to March 2013. From a total of 37 papers, 26 (38 cases) were extracted from the database for systematic review.

Calcifying odontogenic cyst with atypical features

The calcifying odontogenic cyst (COC) was first delineated in 1962. It is a rare developmental odontogenic cyst with notable presence of histopathological features which include a cystic lining demonstrating characteristic “Ghost” epithelial cells with a propensity to calcify. In addition, the COC may be associated with other recognized odontogenic tumors. This gives rise to a spectrum of variants of COC according to clinical, histopathological, and radiological characteristics. Very few reports have actually captured the actual transformation while most reported cases are documents of co-existing lesions. This article presents one such entity, where the asymptomatic presentation misled the diagnosis and on histopathological examination revealed the COC with areas suggestive of adenomatoid odontogenic tumor.