Gastrointestinal stromal tumour and hypoglycemia in a Fjord pony: case report

Gastrointestinal stromal tumors with Kit gene mutation in 4 guinea pigs (Cavia porcellus)

Gastrointestinal stromal tumors (GISTs) have been rarely reported in guinea pigs. We aimed to characterize the clinical and pathological features of GISTs in 4 guinea pigs and investigate the presence of mutations in exon 11 of the KIT proto-oncogene receptor tyrosine kinase (Kit) gene. Two subjects were male and 2 were female; 2 were 6 years old, 1 was 7 years old, and 1 was of an unknown age. Three cases had primary gastric tumors, whereas 1 had a primary small intestinal tumor. All cases had tumors that extended from the submucosa to the serosa with extraluminal growth. A gastric tumor had gastric, pancreatic, and cecal metastases. Histologically, the tumors were sharply demarcated and composed of spindle cells arranged in bundles, intermixed with small amounts of collagenous stroma. The tumor cells had mild atypia with few mitotic figures (0-5/50 high power fields, 7.95 mm²) and were immunolabeled for KIT and Discovered-on-GIST 1 (DOG1). All cases had mutations in exon 11 of the Kit gene. These findings indicate that GISTs in guinea pigs are similar to those in humans and dogs. GISTs in guinea pigs are potentially malignant submucosal tumors with KIT- and DOG1-immunolabeling, exon 11 KIT mutations, and the possibility of metastasis.

Neoplasia in 125 donkeys (Equus asinus): literature review and a survey of five veterinary schools in the United States and Canada

A diagnosis of neoplasia was noted in 125 of 357 donkeys (35%) in our review of medical records from 5 veterinary schools in the United States and Canada. Equine sarcoid was the most common tumor in our study, accounting for 72% of all tumors and 82% of cutaneous tumors. Soft-tissue sarcomas were the second most common skin tumors. All other types of neoplasia were rare. Important differences in the occurrence of neoplasia in donkeys compared to horses included the rarity or absence of squamous cell carcinoma in any organ system and gray horse melanoma. Lymphosarcoma, the most common malignant tumor in horses, appears to be very rare in donkeys. We report several tumors in donkeys including melanocytoma, peripheral nerve sheath tumor, and gastrointestinal stromal tumor. Our data demonstrate commonalities as well as differences in neoplastic diseases of donkeys and horses. Understanding differences in carcinogenesis among these 2 closely related species can inform researchers pursuing pathogenic mechanisms of equine disease and inform veterinary diagnosticians regarding tumor prevalence.

Colonic gastrointestinal stromal tumor resulting in recurrent colic and hematochezia in a warmblood gelding

A 14-year-old Trakehner gelding was evaluated for recurrent colic, with episodes occurring over 1 year. Signs were consistent with intermittent ascending colon obstruction and hematochezia. Necropsy examination revealed an ulcerated mass extending into the lumen of the right dorsal ascending colon. Gross and histologic appearance and immunoreactivity to c-kit (CD117), desmin, vimentin, and smooth muscle actin, were consistent with a diagnosis of gastrointestinal stromal tumor.

A KIT-positive gastrointestinal stromal tumor in a ferret (Mustela putorius furo)

A 1.5-year-old, neutered, male ferret (Mustela putorius furo) was presented with sudden lethargy, anorexia, and diarrhea. Clinical and radiographic examinations revealed an intra-abdominal mass. An explorative laparotomy was performed. A neoplasm, located in the ileum wall, was submitted for histopathologic examination. The tumor consisted of weakly eosinophilic spindle cells arranged in a compact pattern with haphazardly interlacing bundles. Neoplastic cells labeled positively for KIT (cluster of differentiation 117, stem cell factor receptor) and vimentin. Based on histologic and immunohistologic results, this tumor was diagnosed as a gastrointestinal stromal tumor. Results suggest that this ferret tumor shares strong similarities with the canine and human counterparts.