Gastrointestinal Mast Cell Tumor in an African Dormouse (Graphiurus sp.)

SIMPLE SUMMARY: The African dormice, also known as micro squirrels, are now becoming more and more popular as they present as laboratory animals, exhibited animals, or pets. However, we know very little about the diseases in these tiny rodents, such as tumors or infectious microorganisms. A 3-year-old, male African dormouse was taken to the veterinary clinic after showing vomiting and anorexia. A stomach lesion was noted through imaging examinations. The patient died after being treated for 2 months. The veterinary pathologist diagnosed the lesion as a gastric mast cell tumor, cancer occurs mostly in cats and rarely in other animals. This is the first time that a mast cell tumor is diagnosed in an African dormouse. We suggest that the mast cell tumor in digestive tracts should be listed in the differential diagnoses when an elder African dormouse or other small rodent shows chronic digestive signs. ABSTRACT: Mast cell tumors (MCTs) are well-known neoplasms derived from either mucosal or connective tissue mast cells. While well studied in several domestic species, MCTs are rarely documented in rodents. A three-year-old, male African dormouse (Graphiurus sp.) presented with a history of vomiting and anorexia for 3 months. Sonography revealed thickened gastric mucosa and hyperperistalsis. The patient died after receiving symptomatic treatment for 2 months. At necropsy, locally extensive, pale, thickened mucosal foci obscuring the first half of the stomach lumen was noted. Histological examination revealed moderately polymorphic, round, oval to spindle cells with amphophilic cytoplasmic granules infiltrating the mucosa to tunica muscularis, with moderate numbers of eosinophils. The mucosa was severely ulcerated with the proliferation of granulation tissue. The granules in most tumor cells exhibited metachromasia with the toluidine blue stain. Neoplastic cells revealed positive membranous immunoreactivity to KIT. Herein, we report the first case report of MCT in dormouse but also the first gastrointestinal MCT in a rodent species.