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.