Oral Neoplasia in Rabbits

In the literature

Miwa Y, Nakata M, Chambers JK, Uchida K. Spontaneous oral tumours in 18 rabbits (2005-2015). J Small Anim Pract. 2019. doi: 10.1111/jsap.13082

The Research …

Most clinical information on pet rabbits focuses on dental disease and facial abscesses; information on oral neoplasia in the literature is limited for these animals. This study retrospectively reviewed records from a population of pet rabbits in Japan over a 10-year period.

Rabbits have special anatomic and physiologic characteristics in relation to their mouths. These include incisor and cheek teeth being elodont and hypsodont, with their teeth continuing to grow throughout the rabbit’s lifetime.^1,2 Rabbits also have characteristic morphology of the maxilla and mandible, which allows for only a very small and narrow opening of the mouth.^1-2 These anatomic considerations can affect the clinician’s ability to perform an oral examination, testing, and treatment in rabbits with oral disease. 

Clinical signs of oral neoplasia in rabbits may be similar or identical to those of dental disease. Common clinical signs include dysphagia, ptyalism, weight loss, anorexia, and oral hemorrhage.^1,3-5 Physical examination findings can include oral mass, malocclusion, ulceration, and abnormal odor and/or drainage.^1,3-5

A thorough oral examination with the patient under sedation or general anesthesia is one of the most important diagnostic evaluations. Visual examination of the mouth of an awake rabbit is inherently limited and will not allow a thorough evaluation of the oral cavity. Diagnostic imaging (eg, skull and thoracic radiography, CT) for evaluation of masses involving the mouth or head can be useful. 

Blood work changes in this study were determined to be nonspecific for oral neoplasia. Definitive diagnosis requires either a cytologic sample (eg, fine-needle aspirate), soft tissue biopsy, or surgical resection and histopathology. 

In this study, 13 different tumor types were diagnosed in 18 rabbits: squamous cell carcinoma (n = 3), ameloblastoma (n = 2), fibrosarcoma (n = 2), osteosarcoma (n = 2), cementoma (n = 1), complex odontoma (n = 1), giant cell epulis (n = 1), sarcoma (n = 1), chondrosarcoma (n = 1), trichoepithelioma (n = 1), papilloma (n = 1), malignant melanoma (n = 1), and basal cell carcinoma (n = 1).

Treatment of oral neoplasia in the rabbits in this study included surgical debulking of the mass or an attempt at surgical resection.^3-5 Often, it was not possible to obtain clean margins at the time of surgery due to the aforementioned anatomic considerations of this species. Radiation therapy was performed in several patients in this study with positive clinical results. Tumor type may help determine response to certain treatment modalities. Several patients experienced tumor recurrence. Many of the rabbits required regular dental care (eg, trimming or adjustment of the incisor or cheek teeth) to manage overgrowth or malocclusion.

… The Takeaways

Key pearls to put into practice:

• Oral tumors are uncommon in rabbits as compared with some other small mammal species (eg, hedgehogs, ferrets); however, the rate of occurrence in rabbits may be similar to that of dogs.

• Age and sex predisposition may exist in rabbits with oral neoplasia. Middle- to older-age male rabbits may have higher risk for oral neoplasia.

• Clinical signs of oral neoplasia in rabbits are often similar to those of dental disease, which is a more common condition. Clinical signs include dysphagia, dropping of food from the mouth, anorexia, malocclusion, ptyalism, and oral hemorrhage. Diagnostics such as imaging, cytology, and/or histopathology are required for definitive diagnosis.